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coredump: sanitize the setting of signal->group_exit_code 

Now that the coredumping process can be SIGKILL'ed, the setting of
->group_exit_code in do_coredump() can race with complete_signal() and
SIGKILL or 0x80 can be "lost", or wait(status) can report status ==
SIGKILL | 0x80.

But the main problem is that it is not clear to me what should we do if
binfmt->core_dump() succeeds but SIGKILL was sent, that is why this patch
comes as a separate change.

This patch adds 0x80 if ->core_dump() succeeds and the process was not
killed.  But perhaps we can (should?) re-set ->group_exit_code changed by
SIGKILL back to "siginfo->si_signo |= 0x80" in case when core_dumped == T.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Tested-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Neil Horman <nhorman@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Roland McGrath <roland@hack.frob.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2013-04-30 15:28:13 -07:00 committed by Linus Torvalds
parent 6cd8f0acae
commit acdedd99b0
1 changed files with 6 additions and 5 deletions
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11
fs/coredump.c
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@ -390,12 +390,14 @@ static int coredump_wait(int exit_code, struct core_state *core_state)
return core_waiters;
}
static void coredump_finish(struct mm_struct *mm)
static void coredump_finish(struct mm_struct *mm, bool core_dumped)
{
struct core_thread *curr, *next;
struct task_struct *task;
spin_lock_irq(&current->sighand->siglock);
if (core_dumped && !__fatal_signal_pending(current))
current->signal->group_exit_code |= 0x80;
current->signal->group_exit_task = NULL;
current->signal->flags = SIGNAL_GROUP_EXIT;
spin_unlock_irq(&current->sighand->siglock);
@ -480,6 +482,7 @@ void do_coredump(siginfo_t *siginfo)
int ispipe;
struct files_struct *displaced;
bool need_nonrelative = false;
bool core_dumped = false;
static atomic_t core_dump_count = ATOMIC_INIT(0);
struct coredump_params cprm = {
.siginfo = siginfo,
@ -638,9 +641,7 @@ void do_coredump(siginfo_t *siginfo)
goto close_fail;
if (displaced)
put_files_struct(displaced);
retval = binfmt->core_dump(&cprm);
if (retval)
current->signal->group_exit_code |= 0x80;
core_dumped = binfmt->core_dump(&cprm);
if (ispipe && core_pipe_limit)
wait_for_dump_helpers(cprm.file);
@ -653,7 +654,7 @@ fail_dropcount:
fail_unlock:
kfree(cn.corename);
fail_corename:
coredump_finish(mm);
coredump_finish(mm, core_dumped);
revert_creds(old_cred);
fail_creds:
put_cred(cred);