linux/fs/proc
Dmitry Vyukov e41d58185f fault-inject: support systematic fault injection
Add /proc/self/task/<current-tid>/fail-nth file that allows failing
0-th, 1-st, 2-nd and so on calls systematically.
Excerpt from the added documentation:

 "Write to this file of integer N makes N-th call in the current task
  fail (N is 0-based). Read from this file returns a single char 'Y' or
  'N' that says if the fault setup with a previous write to this file
  was injected or not, and disables the fault if it wasn't yet injected.
  Note that this file enables all types of faults (slab, futex, etc).
  This setting takes precedence over all other generic settings like
  probability, interval, times, etc. But per-capability settings (e.g.
  fail_futex/ignore-private) take precedence over it. This feature is
  intended for systematic testing of faults in a single system call. See
  an example below"

Why add a new setting:
1. Existing settings are global rather than per-task.
   So parallel testing is not possible.
2. attr->interval is close but it depends on attr->count
   which is non reset to 0, so interval does not work as expected.
3. Trying to model this with existing settings requires manipulations
   of all of probability, interval, times, space, task-filter and
   unexposed count and per-task make-it-fail files.
4. Existing settings are per-failure-type, and the set of failure
   types is potentially expanding.
5. make-it-fail can't be changed by unprivileged user and aggressive
   stress testing better be done from an unprivileged user.
   Similarly, this would require opening the debugfs files to the
   unprivileged user, as he would need to reopen at least times file
   (not possible to pre-open before dropping privs).

The proposed interface solves all of the above (see the example).

We want to integrate this into syzkaller fuzzer.  A prototype has found
10 bugs in kernel in first day of usage:

  https://groups.google.com/forum/#!searchin/syzkaller/%22FAULT_INJECTION%22%7Csort:relevance

I've made the current interface work with all types of our sandboxes.
For setuid the secret sauce was prctl(PR_SET_DUMPABLE, 1, 0, 0, 0) to
make /proc entries non-root owned.  So I am fine with the current
version of the code.

[akpm@linux-foundation.org: fix build]
Link: http://lkml.kernel.org/r/20170328130128.101773-1-dvyukov@google.com
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-12 16:26:01 -07:00
..
Kconfig fs, proc: add help for CONFIG_PROC_CHILDREN 2015-07-17 16:39:52 -07:00
Makefile fs/proc: Add compiler check for -Wno-override-init to support gcc < 4.2 2016-08-03 12:45:23 -04:00
array.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
base.c fault-inject: support systematic fault injection 2017-07-12 16:26:01 -07:00
cmdline.c
consoles.c
cpuinfo.c
devices.c
fd.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/signal.h> 2017-03-02 08:42:29 +01:00
fd.h proc: unsigned file descriptors 2016-09-27 18:47:38 -04:00
generic.c fs/proc/generic.c: switch to ida_simple_get/remove 2017-07-10 16:32:34 -07:00
inode.c fs/proc/inode.c: remove cast from memory allocation 2017-05-08 17:15:10 -07:00
internal.h Merge branch 'rebased-statx' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-03-03 11:38:56 -08:00
interrupts.c
kcore.c fs/proc: kcore: use kcore_list type to check for vmalloc/module address 2017-06-20 12:42:57 +01:00
kmsg.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
loadavg.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/stat.h> 2017-03-02 08:42:34 +01:00
meminfo.c meminfo: break apart a very long seq_printf with #ifdefs 2016-10-07 18:46:30 -07:00
namespaces.c pidns: expose task pid_ns_for_children to userspace 2017-05-08 17:15:12 -07:00
nommu.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
page.c mm: fix KPF_SWAPCACHE in /proc/kpageflags 2017-02-07 12:08:32 -08:00
proc_net.c Merge branch 'rebased-statx' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-03-03 11:38:56 -08:00
proc_sysctl.c sysctl: add unsigned int range support 2017-07-12 16:26:00 -07:00
proc_tty.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
root.c Merge branch 'rebased-statx' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-03-03 11:38:56 -08:00
self.c vfs: remove ".readlink = generic_readlink" assignments 2016-12-09 16:45:04 +01:00
softirqs.c
stat.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
task_mmu.c fs/proc/task_mmu.c: remove obsolete comment in show_map_vma() 2017-07-10 16:32:32 -07:00
task_nommu.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/mm.h> 2017-03-02 08:42:28 +01:00
thread_self.c vfs: remove ".readlink = generic_readlink" assignments 2016-12-09 16:45:04 +01:00
uptime.c sched/cputime: Convert kcpustat to nsecs 2017-02-01 09:13:47 +01:00
version.c
vmcore.c userfaultfd: non-cooperative: add event for memory unmaps 2017-02-24 17:46:55 -08:00