Commit Graph

592 Commits

Author SHA1 Message Date
Weikang Shi 2e58f57d85 kernel/signal.c: fix a comment error
Because get_signal_to_deliver() was renamed to get_signal() the
comment should be fixed.

Link: http://lkml.kernel.org/r/1539179128-45709-1-git-send-email-swkhack@gmail.com
Signed-off-by: Weikang Shi <swkhack@gmail.com>
Reported-by: Christian Brauner <christian@brauner.io>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-10-31 08:54:14 -07:00
Linus Torvalds 4dcb9239da Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timekeeping updates from Thomas Gleixner:
 "The timers and timekeeping departement provides:

   - Another large y2038 update with further preparations for providing
     the y2038 safe timespecs closer to the syscalls.

   - An overhaul of the SHCMT clocksource driver

   - SPDX license identifier updates

   - Small cleanups and fixes all over the place"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (31 commits)
  tick/sched : Remove redundant cpu_online() check
  clocksource/drivers/dw_apb: Add reset control
  clocksource: Remove obsolete CLOCKSOURCE_OF_DECLARE
  clocksource/drivers: Unify the names to timer-* format
  clocksource/drivers/sh_cmt: Add R-Car gen3 support
  dt-bindings: timer: renesas: cmt: document R-Car gen3 support
  clocksource/drivers/sh_cmt: Properly line-wrap sh_cmt_of_table[] initializer
  clocksource/drivers/sh_cmt: Fix clocksource width for 32-bit machines
  clocksource/drivers/sh_cmt: Fixup for 64-bit machines
  clocksource/drivers/sh_tmu: Convert to SPDX identifiers
  clocksource/drivers/sh_mtu2: Convert to SPDX identifiers
  clocksource/drivers/sh_cmt: Convert to SPDX identifiers
  clocksource/drivers/renesas-ostm: Convert to SPDX identifiers
  clocksource: Convert to using %pOFn instead of device_node.name
  tick/broadcast: Remove redundant check
  RISC-V: Request newstat syscalls
  y2038: signal: Change rt_sigtimedwait to use __kernel_timespec
  y2038: socket: Change recvmmsg to use __kernel_timespec
  y2038: sched: Change sched_rr_get_interval to use __kernel_timespec
  y2038: utimes: Rework #ifdef guards for compat syscalls
  ...
2018-10-25 11:14:36 -07:00
Linus Torvalds ba9f6f8954 Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull siginfo updates from Eric Biederman:
 "I have been slowly sorting out siginfo and this is the culmination of
  that work.

  The primary result is in several ways the signal infrastructure has
  been made less error prone. The code has been updated so that manually
  specifying SEND_SIG_FORCED is never necessary. The conversion to the
  new siginfo sending functions is now complete, which makes it
  difficult to send a signal without filling in the proper siginfo
  fields.

  At the tail end of the patchset comes the optimization of decreasing
  the size of struct siginfo in the kernel from 128 bytes to about 48
  bytes on 64bit. The fundamental observation that enables this is by
  definition none of the known ways to use struct siginfo uses the extra
  bytes.

  This comes at the cost of a small user space observable difference.
  For the rare case of siginfo being injected into the kernel only what
  can be copied into kernel_siginfo is delivered to the destination, the
  rest of the bytes are set to 0. For cases where the signal and the
  si_code are known this is safe, because we know those bytes are not
  used. For cases where the signal and si_code combination is unknown
  the bits that won't fit into struct kernel_siginfo are tested to
  verify they are zero, and the send fails if they are not.

  I made an extensive search through userspace code and I could not find
  anything that would break because of the above change. If it turns out
  I did break something it will take just the revert of a single change
  to restore kernel_siginfo to the same size as userspace siginfo.

  Testing did reveal dependencies on preferring the signo passed to
  sigqueueinfo over si->signo, so bit the bullet and added the
  complexity necessary to handle that case.

  Testing also revealed bad things can happen if a negative signal
  number is passed into the system calls. Something no sane application
  will do but something a malicious program or a fuzzer might do. So I
  have fixed the code that performs the bounds checks to ensure negative
  signal numbers are handled"

* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (80 commits)
  signal: Guard against negative signal numbers in copy_siginfo_from_user32
  signal: Guard against negative signal numbers in copy_siginfo_from_user
  signal: In sigqueueinfo prefer sig not si_signo
  signal: Use a smaller struct siginfo in the kernel
  signal: Distinguish between kernel_siginfo and siginfo
  signal: Introduce copy_siginfo_from_user and use it's return value
  signal: Remove the need for __ARCH_SI_PREABLE_SIZE and SI_PAD_SIZE
  signal: Fail sigqueueinfo if si_signo != sig
  signal/sparc: Move EMT_TAGOVF into the generic siginfo.h
  signal/unicore32: Use force_sig_fault where appropriate
  signal/unicore32: Generate siginfo in ucs32_notify_die
  signal/unicore32: Use send_sig_fault where appropriate
  signal/arc: Use force_sig_fault where appropriate
  signal/arc: Push siginfo generation into unhandled_exception
  signal/ia64: Use force_sig_fault where appropriate
  signal/ia64: Use the force_sig(SIGSEGV,...) in ia64_rt_sigreturn
  signal/ia64: Use the generic force_sigsegv in setup_frame
  signal/arm/kvm: Use send_sig_mceerr
  signal/arm: Use send_sig_fault where appropriate
  signal/arm: Use force_sig_fault where appropriate
  ...
2018-10-24 11:22:39 +01:00
Eric W. Biederman a36700589b signal: Guard against negative signal numbers in copy_siginfo_from_user32
While fixing an out of bounds array access in known_siginfo_layout
reported by the kernel test robot it became apparent that the same bug
exists in siginfo_layout and affects copy_siginfo_from_user32.

The straight forward fix that makes guards against making this mistake
in the future and should keep the code size small is to just take an
unsigned signal number instead of a signed signal number, as I did to
fix known_siginfo_layout.

Cc: stable@vger.kernel.org
Fixes: cc731525f2 ("signal: Remove kernel interal si_code magic")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-10-10 20:34:14 -05:00
Eric W. Biederman b2a2ab527d signal: Guard against negative signal numbers in copy_siginfo_from_user
The bounds checks in known_siginfo_layout only guards against positive
numbers that are too large, large negative can slip through and
can cause out of bounds accesses.

Ordinarily this is not a concern because early in signal processing
the signal number is filtered with valid_signal which ensures it
is a small positive signal number, but copy_siginfo_from_user
is called before this check is performed.

[   73.031126] BUG: unable to handle kernel paging request at ffffffff6281bcb6
[   73.032038] PGD 3014067 P4D 3014067 PUD 0
[   73.032565] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI
[   73.033287] CPU: 0 PID: 732 Comm: trinity-c3 Tainted: G        W       T 4.19.0-rc1-00077-g4ce5f9c #1
[   73.034423] RIP: 0010:copy_siginfo_from_user+0x4d/0xd0
[   73.034908] Code: 00 8b 53 08 81 fa 80 00 00 00 0f 84 90 00 00 00 85 d2 7e 2d 48 63 0b 83 f9 1f 7f 1c 8d 71 ff bf d8 04 01 50 48 0f a3 f7 73 0e <0f> b6 8c 09 20 bb 81 82 39 ca 7f 15 eb 68 31 c0 83 fa 06 7f 0c eb
[   73.036665] RSP: 0018:ffff88001b8f7e20 EFLAGS: 00010297
[   73.037160] RAX: 0000000000000000 RBX: ffff88001b8f7e90 RCX: fffffffff00000cb
[   73.037865] RDX: 0000000000000001 RSI: 00000000f00000ca RDI: 00000000500104d8
[   73.038546] RBP: ffff88001b8f7e80 R08: 0000000000000000 R09: 0000000000000000
[   73.039201] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000008
[   73.039874] R13: 00000000000002dc R14: 0000000000000000 R15: 0000000000000000
[   73.040613] FS:  000000000104a880(0000) GS:ffff88001f000000(0000) knlGS:0000000000000000
[   73.041649] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   73.042405] CR2: ffffffff6281bcb6 CR3: 000000001cb52003 CR4: 00000000001606b0
[   73.043351] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   73.044286] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
[   73.045221] Call Trace:
[   73.045556]  __x64_sys_rt_tgsigqueueinfo+0x34/0xa0
[   73.046199]  do_syscall_64+0x1a4/0x390
[   73.046708]  ? vtime_user_enter+0x61/0x80
[   73.047242]  ? __context_tracking_enter+0x4e/0x60
[   73.047714]  ? __context_tracking_enter+0x4e/0x60
[   73.048278]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Therefore fix known_siginfo_layout to take an unsigned signal number
instead of a signed signal number.  All valid signal numbers are small
positive numbers so they will not be affected, but invalid negative
signal numbers will now become large positive signal numbers and will
not be used as indices into the sig_sicodes array.

Making the signal number unsigned makes it difficult for similar mistakes to
happen in the future.

Fixes: 4ce5f9c9e7 ("signal: Use a smaller struct siginfo in the kernel")
Inspired-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-10-10 20:28:33 -05:00
Eric W. Biederman 601d5abfea signal: In sigqueueinfo prefer sig not si_signo
Andrei Vagin <avagin@gmail.com> reported:

> Accoding to the man page, the user should not set si_signo, it has to be set
> by kernel.
>
> $ man 2 rt_sigqueueinfo
>
>     The uinfo argument specifies the data to accompany  the  signal.   This
>        argument  is  a  pointer to a structure of type siginfo_t, described in
>        sigaction(2) (and defined  by  including  <sigaction.h>).   The  caller
>        should set the following fields in this structure:
>
>        si_code
>               This  must  be  one of the SI_* codes in the Linux kernel source
>               file include/asm-generic/siginfo.h, with  the  restriction  that
>               the  code  must  be  negative (i.e., cannot be SI_USER, which is
>               used by the kernel to indicate a signal  sent  by  kill(2))  and
>               cannot  (since  Linux  2.6.39) be SI_TKILL (which is used by the
>               kernel to indicate a signal sent using tgkill(2)).
>
>        si_pid This should be set to a process ID, typically the process ID  of
>               the sender.
>
>        si_uid This  should  be set to a user ID, typically the real user ID of
>               the sender.
>
>        si_value
>               This field contains the user data to accompany the signal.   For
>               more information, see the description of the last (union sigval)
>               argument of sigqueue(3).
>
>        Internally, the kernel sets the si_signo field to the  value  specified
>        in  sig,  so that the receiver of the signal can also obtain the signal
>        number via that field.
>
> On Tue, Sep 25, 2018 at 07:19:02PM +0200, Eric W. Biederman wrote:
>>
>> If there is some application that calls sigqueueinfo directly that has
>> a problem with this added sanity check we can revisit this when we see
>> what kind of crazy that application is doing.
>
>
> I already know two "applications" ;)
>
> https://github.com/torvalds/linux/blob/master/tools/testing/selftests/ptrace/peeksiginfo.c
> https://github.com/checkpoint-restore/criu/blob/master/test/zdtm/static/sigpending.c
>
> Disclaimer: I'm the author of both of them.

Looking at the kernel code the historical behavior has alwasy been to prefer
the signal number passed in by the kernel.

So sigh.  Implmenet __copy_siginfo_from_user and __copy_siginfo_from_user32 to
take that signal number and prefer it.  The user of ptrace will still
use copy_siginfo_from_user and copy_siginfo_from_user32 as they do not and
never have had a signal number there.

Luckily this change has never made it farther than linux-next.

Fixes: e75dc036c4 ("signal: Fail sigqueueinfo if si_signo != sig")
Reported-by: Andrei Vagin <avagin@gmail.com>
Tested-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-10-08 09:35:26 +02:00
Eric W. Biederman 4ce5f9c9e7 signal: Use a smaller struct siginfo in the kernel
We reserve 128 bytes for struct siginfo but only use about 48 bytes on
64bit and 32 bytes on 32bit.  Someday we might use more but it is unlikely
to be anytime soon.

Userspace seems content with just enough bytes of siginfo to implement
sigqueue.  Or in the case of checkpoint/restart reinjecting signals
the kernel has sent.

Reducing the stack footprint and the work to copy siginfo around from
2 cachelines to 1 cachelines seems worth doing even if I don't have
benchmarks to show a performance difference.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-10-03 16:50:39 +02:00
Eric W. Biederman ae7795bc61 signal: Distinguish between kernel_siginfo and siginfo
Linus recently observed that if we did not worry about the padding
member in struct siginfo it is only about 48 bytes, and 48 bytes is
much nicer than 128 bytes for allocating on the stack and copying
around in the kernel.

The obvious thing of only adding the padding when userspace is
including siginfo.h won't work as there are sigframe definitions in
the kernel that embed struct siginfo.

So split siginfo in two; kernel_siginfo and siginfo.  Keeping the
traditional name for the userspace definition.  While the version that
is used internally to the kernel and ultimately will not be padded to
128 bytes is called kernel_siginfo.

The definition of struct kernel_siginfo I have put in include/signal_types.h

A set of buildtime checks has been added to verify the two structures have
the same field offsets.

To make it easy to verify the change kernel_siginfo retains the same
size as siginfo.  The reduction in size comes in a following change.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-10-03 16:47:43 +02:00
Eric W. Biederman 4cd2e0e70a signal: Introduce copy_siginfo_from_user and use it's return value
In preparation for using a smaller version of siginfo in the kernel
introduce copy_siginfo_from_user and use it when siginfo is copied from
userspace.

Make the pattern for using copy_siginfo_from_user and
copy_siginfo_from_user32 to capture the return value and return that
value on error.

This is a necessary prerequisite for using a smaller siginfo
in the kernel than the kernel exports to userspace.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-10-03 16:47:15 +02:00
Eric W. Biederman f283801851 signal: Remove the need for __ARCH_SI_PREABLE_SIZE and SI_PAD_SIZE
Rework the defintion of struct siginfo so that the array padding
struct siginfo to SI_MAX_SIZE can be placed in a union along side of
the rest of the struct siginfo members.  The result is that we no
longer need the __ARCH_SI_PREAMBLE_SIZE or SI_PAD_SIZE definitions.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-10-03 16:46:43 +02:00
Eric W. Biederman e75dc036c4 signal: Fail sigqueueinfo if si_signo != sig
The kernel needs to validate that the contents of struct siginfo make
sense as siginfo is copied into the kernel, so that the proper union
members can be put in the appropriate locations.  The field si_signo
is a fundamental part of that validation.  As such changing the
contents of si_signo after the validation make no sense and can result
in nonsense values in the kernel.

As such simply fail if someone is silly enough to set si_signo out of
sync with the signal number passed to sigqueueinfo.

I don't expect a problem as glibc's sigqueue implementation sets
"si_signo = sig" and CRIU just returns to the kernel what the kernel
gave to it.

If there is some application that calls sigqueueinfo directly that has
a problem with this added sanity check we can revisit this when we see
what kind of crazy that application is doing.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-10-03 16:46:28 +02:00
Eric W. Biederman 018303a931 signal/sparc: Move EMT_TAGOVF into the generic siginfo.h
When moving all of the architectures specific si_codes into
siginfo.h, I apparently overlooked EMT_TAGOVF.  Move it now.

Remove the now redundant test in siginfo_layout for SIGEMT
as now NSIGEMT is always defined.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-10-03 16:42:13 +02:00
Will Deacon 22839869f2 signal: Introduce COMPAT_SIGMINSTKSZ for use in compat_sys_sigaltstack
The sigaltstack(2) system call fails with -ENOMEM if the new alternative
signal stack is found to be smaller than SIGMINSTKSZ. On architectures
such as arm64, where the native value for SIGMINSTKSZ is larger than
the compat value, this can result in an unexpected error being reported
to a compat task. See, for example:

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=904385

This patch fixes the problem by extending do_sigaltstack to take the
minimum signal stack size as an additional parameter, allowing the
native and compat system call entry code to pass in their respective
values. COMPAT_SIGMINSTKSZ is just defined as SIGMINSTKSZ if it has not
been defined by the architecture.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Reported-by: Steve McIntyre <steve.mcintyre@arm.com>
Tested-by: Steve McIntyre <93sam@debian.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2018-10-01 11:43:55 +01:00
Eric W. Biederman fb50f5a401 signal: Pair exports with their functions
For readability and consistency with the other exports in
kernel/signal.c pair the exports of signal sending functions with
their functions, instead of having the exports in one big clump.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-09-16 16:56:54 +02:00
Eric W. Biederman b21c5bd562 signal: Remove specific_send_sig_info
This function is static and it only has two callers.  As
specific_send_sig_info is only called twice remembering what
specific_send_sig_info does when reading the code is difficutl and it
makes it hard to see which sending sending functions are equivalent to
which others.

So remove specific_send_sig_info to make the code easier to read.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-09-16 16:09:45 +02:00
Eric W. Biederman 4ff4c31a6e signal: Remove SEND_SIG_FORCED
There are no more users of SEND_SIG_FORCED so it may be safely removed.

Remove the definition of SEND_SIG_FORCED, it's use in is_si_special,
it's use in TP_STORE_SIGINFO, and it's use in __send_signal as without
any users the uses of SEND_SIG_FORCED are now unncessary.

This makes the code simpler, easier to understand and use.  Users of
signal sending functions now no longer need to ask themselves do I
need to use SEND_SIG_FORCED.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-09-11 21:19:48 +02:00
Eric W. Biederman f149b31557 signal: Never allocate siginfo for SIGKILL or SIGSTOP
The SIGKILL and SIGSTOP signals are never delivered to userspace so
queued siginfo for these signals can never be observed.  Therefore
remove the chance of failure by never even attempting to allocate
siginfo in those cases.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-09-11 21:19:28 +02:00
Eric W. Biederman 0351505405 signal: Don't send siginfo to kthreads.
Today kernel threads never dequeue siginfo so it is pointless to
enqueue siginfo for them.  The usb gadget mass storage driver goes
one farther and uses SEND_SIG_FORCED to guarantee that no siginfo is
even enqueued.

Generalize the optimization of the usb mass storage driver and never
perform an unnecessary allocation when delivering signals to kthreads.

Switch the mass storage driver from sending signals with
SEND_SIG_FORCED to SEND_SIG_PRIV.  As using SEND_SIG_FORCED is now
unnecessary.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-09-11 21:19:22 +02:00
Eric W. Biederman 3597dfe01d signal: Always deliver the kernel's SIGKILL and SIGSTOP to a pid namespace init
Instead of playing whack-a-mole and changing SEND_SIG_PRIV to
SEND_SIG_FORCED throughout the kernel to ensure a pid namespace init
gets signals sent by the kernel, stop allowing a pid namespace init to
ignore SIGKILL or SIGSTOP sent by the kernel.  A pid namespace init is
only supposed to be able to ignore signals sent from itself and
children with SIG_DFL.

Fixes: 921cf9f630 ("signals: protect cinit from unblocked SIG_DFL signals")
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-09-11 21:19:00 +02:00
Eric W. Biederman 86989c41b5 signal: Always ignore SIGKILL and SIGSTOP sent to the global init
If the first process started (aka /sbin/init) receives a SIGKILL it
will panic the system if it is delivered.  Making the system unusable
and undebugable.  It isn't much better if the first process started
receives SIGSTOP.

So always ignore SIGSTOP and SIGKILL sent to init.

This is done in a separate clause in sig_task_ignored as force_sig_info
can clear SIG_UNKILLABLE and this protection should work even then.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-09-11 21:18:15 +02:00
Arnd Bergmann 49c39f8464 y2038: signal: Change rt_sigtimedwait to use __kernel_timespec
This changes sys_rt_sigtimedwait() to use get_timespec64(), changing
the timeout type to __kernel_timespec, which will be changed to use
a 64-bit time_t in the future. Since the do_sigtimedwait() core
function changes, we also have to modify the compat version of this
system call in the same way.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
2018-08-29 15:42:25 +02:00
Arnd Bergmann 9afc5eee65 y2038: globally rename compat_time to old_time32
Christoph Hellwig suggested a slightly different path for handling
backwards compatibility with the 32-bit time_t based system calls:

Rather than simply reusing the compat_sys_* entry points on 32-bit
architectures unchanged, we get rid of those entry points and the
compat_time types by renaming them to something that makes more sense
on 32-bit architectures (which don't have a compat mode otherwise),
and then share the entry points under the new name with the 64-bit
architectures that use them for implementing the compatibility.

The following types and interfaces are renamed here, and moved
from linux/compat_time.h to linux/time32.h:

old				new
---				---
compat_time_t			old_time32_t
struct compat_timeval		struct old_timeval32
struct compat_timespec		struct old_timespec32
struct compat_itimerspec	struct old_itimerspec32
ns_to_compat_timeval()		ns_to_old_timeval32()
get_compat_itimerspec64()	get_old_itimerspec32()
put_compat_itimerspec64()	put_old_itimerspec32()
compat_get_timespec64()		get_old_timespec32()
compat_put_timespec64()		put_old_timespec32()

As we already have aliases in place, this patch addresses only the
instances that are relevant to the system call interface in particular,
not those that occur in device drivers and other modules. Those
will get handled separately, while providing the 64-bit version
of the respective interfaces.

I'm not renaming the timex, rusage and itimerval structures, as we are
still debating what the new interface will look like, and whether we
will need a replacement at all.

This also doesn't change the names of the syscall entry points, which can
be done more easily when we actually switch over the 32-bit architectures
to use them, at that point we need to change COMPAT_SYSCALL_DEFINEx to
SYSCALL_DEFINEx with a new name, e.g. with a _time32 suffix.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Link: https://lore.kernel.org/lkml/20180705222110.GA5698@infradead.org/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
2018-08-27 14:48:48 +02:00
Linus Torvalds cd9b44f907 Merge branch 'akpm' (patches from Andrew)
Merge more updates from Andrew Morton:

 - the rest of MM

 - procfs updates

 - various misc things

 - more y2038 fixes

 - get_maintainer updates

 - lib/ updates

 - checkpatch updates

 - various epoll updates

 - autofs updates

 - hfsplus

 - some reiserfs work

 - fatfs updates

 - signal.c cleanups

 - ipc/ updates

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (166 commits)
  ipc/util.c: update return value of ipc_getref from int to bool
  ipc/util.c: further variable name cleanups
  ipc: simplify ipc initialization
  ipc: get rid of ids->tables_initialized hack
  lib/rhashtable: guarantee initial hashtable allocation
  lib/rhashtable: simplify bucket_table_alloc()
  ipc: drop ipc_lock()
  ipc/util.c: correct comment in ipc_obtain_object_check
  ipc: rename ipcctl_pre_down_nolock()
  ipc/util.c: use ipc_rcu_putref() for failues in ipc_addid()
  ipc: reorganize initialization of kern_ipc_perm.seq
  ipc: compute kern_ipc_perm.id under the ipc lock
  init/Kconfig: remove EXPERT from CHECKPOINT_RESTORE
  fs/sysv/inode.c: use ktime_get_real_seconds() for superblock stamp
  adfs: use timespec64 for time conversion
  kernel/sysctl.c: fix typos in comments
  drivers/rapidio/devices/rio_mport_cdev.c: remove redundant pointer md
  fork: don't copy inconsistent signal handler state to child
  signal: make get_signal() return bool
  signal: make sigkill_pending() return bool
  ...
2018-08-22 12:34:08 -07:00
Christian Brauner 20ab7218d2 signal: make get_signal() return bool
make get_signal() already behaves like a boolean function.  Let's actually
declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-18-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:51 -07:00
Christian Brauner f99e9d8c5c signal: make sigkill_pending() return bool
sigkill_pending() already behaves like a boolean function.  Let's actually
declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-17-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:51 -07:00
Christian Brauner a19e2c01f7 signal: make legacy_queue() return bool
legacy_queue() already behaves like a boolean function.  Let's actually
declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-16-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:51 -07:00
Christian Brauner acd14e62f0 signal: make wants_signal() return bool
wants_signal() already behaves like a boolean function.  Let's actually
declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-15-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:51 -07:00
Christian Brauner 8f11351eee signal: make flush_sigqueue_mask() void
The return value of flush_sigqueue_mask() is never checked anywhere.

Link: http://lkml.kernel.org/r/20180602103653.18181-14-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:51 -07:00
Christian Brauner 67a48a2447 signal: make unhandled_signal() return bool
unhandled_signal() already behaves like a boolean function.  Let's
actually declare it as such too.  All callers treat it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-13-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:51 -07:00
Christian Brauner 09ae854edb signal: make recalc_sigpending_tsk() return bool
recalc_sigpending_tsk() already behaves like a boolean function.  Let's
actually declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-12-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:51 -07:00
Christian Brauner 938696a829 signal: make has_pending_signals() return bool
has_pending_signals() already behaves like a boolean function.  Let's
actually declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-11-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:51 -07:00
Christian Brauner 6a0cdcd788 signal: make sig_ignored() return bool
sig_ignored() already behaves like a boolean function.  Let's actually
declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-10-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:51 -07:00
Christian Brauner 41aaa48119 signal: make sig_task_ignored() return bool
sig_task_ignored() already behaves like a boolean function.  Let's
actually declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-9-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:50 -07:00
Christian Brauner e4a8b4efbf signal: make sig_handler_ignored() return bool
sig_handler_ignored() already behaves like a boolean function.  Let's
actually declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-8-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:50 -07:00
Christian Brauner 2a9b909409 signal: make kill_ok_by_cred() return bool
kill_ok_by_cred() already behaves like a boolean function.  Let's actually
declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-7-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:50 -07:00
Christian Brauner d8f993b3db signal: simplify rt_sigaction()
The goto is not needed and does not add any clarity.  Simply return
-EINVAL on unexpected sigset_t struct size directly.

Link: http://lkml.kernel.org/r/20180602103653.18181-6-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:50 -07:00
Christian Brauner b1d294c803 signal: make do_sigpending() void
do_sigpending() returned 0 unconditionally so it doesn't make sense to
have it return at all.  This allows us to simplify a bunch of syscall
callers.

Link: http://lkml.kernel.org/r/20180602103653.18181-5-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:50 -07:00
Christian Brauner 6527de9533 signal: make may_ptrace_stop() return bool
may_ptrace_stop() already behaves like a boolean function.  Let's actually
declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-4-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:50 -07:00
Christian Brauner bb17fcca07 signal: make kill_as_cred_perm() return bool
kill_as_cred_perm() already behaves like a boolean function.  Let's
actually declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-3-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:50 -07:00
Christian Brauner 52cba1a274 signal: make force_sigsegv() void
Patch series "signal: refactor some functions", v3.

This series refactors a bunch of functions in signal.c to simplify parts
of the code.

The greatest single change is declaring the static do_sigpending() helper
as void which makes it possible to remove a bunch of unnecessary checks in
the syscalls later on.

This patch (of 17):

force_sigsegv() returned 0 unconditionally so it doesn't make sense to have
it return at all. In addition, there are no callers that check
force_sigsegv()'s return value.

Link: http://lkml.kernel.org/r/20180602103653.18181-2-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-22 10:52:50 -07:00
Eric W. Biederman c3ad2c3b02 signal: Don't restart fork when signals come in.
Wen Yang <wen.yang99@zte.com.cn> and majiang <ma.jiang@zte.com.cn>
report that a periodic signal received during fork can cause fork to
continually restart preventing an application from making progress.

The code was being overly pessimistic.  Fork needs to guarantee that a
signal sent to multiple processes is logically delivered before the
fork and just to the forking process or logically delivered after the
fork to both the forking process and it's newly spawned child.  For
signals like periodic timers that are always delivered to a single
process fork can safely complete and let them appear to logically
delivered after the fork().

While examining this issue I also discovered that fork today will miss
signals delivered to multiple processes during the fork and handled by
another thread.  Similarly the current code will also miss blocked
signals that are delivered to multiple process, as those signals will
not appear pending during fork.

Add a list of each thread that is currently forking, and keep on that
list a signal set that records all of the signals sent to multiple
processes.  When fork completes initialize the new processes
shared_pending signal set with it.  The calculate_sigpending function
will see those signals and set TIF_SIGPENDING causing the new task to
take the slow path to userspace to handle those signals.  Making it
appear as if those signals were received immediately after the fork.

It is not possible to send real time signals to multiple processes and
exceptions don't go to multiple processes, which means that that are
no signals sent to multiple processes that require siginfo.  This
means it is safe to not bother collecting siginfo on signals sent
during fork.

The sigaction of a child of fork is initially the same as the
sigaction of the parent process.  So a signal the parent ignores the
child will also initially ignore.  Therefore it is safe to ignore
signals sent to multiple processes and ignored by the forking process.

Signals sent to only a single process or only a single thread and delivered
during fork are treated as if they are received after the fork, and generally
not dealt with.  They won't cause any problems.

V2: Added removal from the multiprocess list on failure.
V3: Use -ERESTARTNOINTR directly
V4: - Don't queue both SIGCONT and SIGSTOP
    - Initialize signal_struct.multiprocess in init_task
    - Move setting of shared_pending to before the new task
      is visible to signals.  This prevents signals from comming
      in before shared_pending.signal is set to delayed.signal
      and being lost.
V5: - rework list add and delete to account for idle threads
v6: - Use sigdelsetmask when removing stop signals

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=200447
Reported-by: Wen Yang <wen.yang99@zte.com.cn> and
Reported-by: majiang <ma.jiang@zte.com.cn>
Fixes: 4a2c7a7837 ("[PATCH] make fork() atomic wrt pgrp/session signals")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-08-09 13:07:01 -05:00
Eric W. Biederman 924de3b8c9 fork: Have new threads join on-going signal group stops
There are only two signals that are delivered to every member of a
signal group: SIGSTOP and SIGKILL.  Signal delivery requires every
signal appear to be delivered either before or after a clone syscall.
SIGKILL terminates the clone so does not need to be considered.  Which
leaves only SIGSTOP that needs to be considered when creating new
threads.

Today in the event of a group stop TIF_SIGPENDING will get set and the
fork will restart ensuring the fork syscall participates in the group
stop.

A fork (especially of a process with a lot of memory) is one of the
most expensive system so we really only want to restart a fork when
necessary.

It is easy so check to see if a SIGSTOP is ongoing and have the new
thread join it immediate after the clone completes.  Making it appear
the clone completed happened just before the SIGSTOP.

The calculate_sigpending function will see the bits set in jobctl and
set TIF_SIGPENDING to ensure the new task takes the slow path to userspace.

V2: The call to task_join_group_stop was moved before the new task is
    added to the thread group list.  This should not matter as
    sighand->siglock is held over both the addition of the threads,
    the call to task_join_group_stop and do_signal_stop.  But the change
    is trivial and it is one less thing to worry about when reading
    the code.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-08-03 20:20:14 -05:00
Eric W. Biederman 088fe47ce9 signal: Add calculate_sigpending()
Add a function calculate_sigpending to test to see if any signals are
pending for a new task immediately following fork.  Signals have to
happen either before or after fork.  Today our practice is to push
all of the signals to before the fork, but that has the downside that
frequent or periodic signals can make fork take much much longer than
normal or prevent fork from completing entirely.

So we need move signals that we can after the fork to prevent that.

This updates the code to set TIF_SIGPENDING on a new task if there
are signals or other activities that have moved so that they appear
to happen after the fork.

As the code today restarts if it sees any such activity this won't
immediately have an effect, as there will be no reason for it
to set TIF_SIGPENDING immediately after the fork.

Adding calculate_sigpending means the code in fork can safely be
changed to not always restart if a signal is pending.

The new calculate_sigpending function sets sigpending if there
are pending bits in jobctl, pending signals, the freezer needs
to freeze the new task or the live kernel patching framework
need the new thread to take the slow path to userspace.

I have verified that setting TIF_SIGPENDING does make a new process
take the slow path to userspace before it executes it's first userspace
instruction.

I have looked at the callers of signal_wake_up and the code paths
setting TIF_SIGPENDING and I don't see anything else that needs to be
handled.  The code probably doesn't need to set TIF_SIGPENDING for the
kernel live patching as it uses a separate thread flag as well.  But
at this point it seems safer reuse the recalc_sigpending logic and get
the kernel live patching folks to sort out their story later.

V2: I have moved the test into schedule_tail where siglock can
    be grabbed and recalc_sigpending can be reused directly.
    Further as the last action of setting up a new task this
    guarantees that TIF_SIGPENDING will be properly set in the
    new process.

    The helper calculate_sigpending takes the siglock and
    uncontitionally sets TIF_SIGPENDING and let's recalc_sigpending
    clear TIF_SIGPENDING if it is unnecessary.  This allows reusing
    the existing code and keeps maintenance of the conditions simple.

    Oleg Nesterov <oleg@redhat.com>  suggested the movement
    and pointed out the need to take siglock if this code
    was going to be called while the new task is discoverable.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-08-03 20:10:31 -05:00
Eric W. Biederman 0729614992 signal: Push pid type down into complete_signal.
This is the bottom and by pushing this down it simplifies the callers
and otherwise leaves things as is.  This is in preparation for allowing
fork to implement better handling of signals set to groups of processes.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-07-21 12:57:35 -05:00
Eric W. Biederman 5a883cee74 signal: Push pid type down into __send_signal
This information is already available in the callers and by pushing it
down it makes the code a little clearer, and allows implementing
better handling of signales set to a group of processes in fork.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-07-21 12:57:35 -05:00
Eric W. Biederman b213984bd3 signal: Push pid type down into send_signal
This information is already available in the callers and by pushing it
down it makes the code a little clearer, and allows better group
signal behavior in fork.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-07-21 12:57:35 -05:00
Eric W. Biederman 40b3b02535 signal: Pass pid type into do_send_sig_info
This passes the information we already have at the call sight into
do_send_sig_info.  Ultimately allowing for better handling of signals
sent to a group of processes during fork.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-07-21 12:57:35 -05:00
Eric W. Biederman 0102498083 signal: Pass pid type into group_send_sig_info
This passes the information we already have at the call sight
into group_send_sig_info.  Ultimatelly allowing for to better handle
signals sent to a group of processes.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-07-21 12:57:35 -05:00
Eric W. Biederman 24122c7f49 signal: Pass pid and pid type into send_sigqueue
Make the code more maintainable by performing more of the signal
related work in send_sigqueue.

A quick inspection of do_timer_create will show that this code path
does not lookup a thread group by a thread's pid.  Making it safe
to find the task pointed to by it_pid with "pid_task(it_pid, type)";

This supports the changes needed in fork to tell if a signal was sent
to a single process or a group of processes.

Having the pid to task transition in signal.c will also make it easier
to sort out races with de_thread and and the thread group leader
exiting when it comes time to address that.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-07-21 10:43:12 -05:00
Anna-Maria Gleixner 59dc6f3c6d signal: Remove no longer required irqsave/restore
Commit a841796f11 ("signal: align __lock_task_sighand() irq disabling and
RCU") introduced a rcu read side critical section with interrupts
disabled. The changelog suggested that a better long-term fix would be "to
make rt_mutex_unlock() disable irqs when acquiring the rt_mutex structure's
->wait_lock".

This long-term fix has been made in commit b4abf91047 ("rtmutex: Make
wait_lock irq safe") for a different reason.

Therefore revert commit a841796f11 ("signal: align >
__lock_task_sighand() irq disabling and RCU") as the interrupt disable
dance is not longer required.

The change was tested on the base of b4abf91047 ("rtmutex: Make wait_lock
irq safe") with a four hour run of rcutorture scenario TREE03 with lockdep
enabled as suggested by Paul McKenney.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: bigeasy@linutronix.de
Link: https://lkml.kernel.org/r/20180525090507.22248-3-anna-maria@linutronix.de
2018-06-10 06:14:01 +02:00