android/android_kernel_xiaomi_sm8450
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coredump: ensure all coredumping tasks have SIGNAL_GROUP_COREDUMP

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task_will_free_mem() is wrong in many ways, and in particular the
SIGNAL_GROUP_COREDUMP check is not reliable: a task can participate in the
coredumping without SIGNAL_GROUP_COREDUMP bit set.

change zap_threads() paths to always set SIGNAL_GROUP_COREDUMP even if
other CLONE_VM processes can't react to SIGKILL.  Fortunately, at least
oom-kill case if fine; it kills all tasks sharing the same mm, so it
should also kill the process which actually dumps the core.

The change in prepare_signal() is not strictly necessary, it just ensures
that the patch does not bring another subtle behavioural change.  But it
reminds us that this SIGNAL_GROUP_EXIT/COREDUMP case needs more changes.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Kyle Walker <kwalker@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Stanislav Kozina <skozina@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
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 2015-11-06 16:32:31 -08:00 committed by Linus Torvalds
parent 9317bb9696
commit 5fa534c987
2 changed files with 7 additions and 7 deletions
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12
fs/coredump.c
View File

@ -280,11 +280,13 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm)
return ispipe; return ispipe;
} }
static int zap_process(struct task_struct *start, int exit_code) static int zap_process(struct task_struct *start, int exit_code, int flags)
{ {
struct task_struct *t; struct task_struct *t;
int nr = 0; int nr = 0;
/* ignore all signals except SIGKILL, see prepare_signal() */
start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
start->signal->group_exit_code = exit_code; start->signal->group_exit_code = exit_code;
start->signal->group_stop_count = 0; start->signal->group_stop_count = 0;
@ -311,10 +313,8 @@ static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
spin_lock_irq(&tsk->sighand->siglock); spin_lock_irq(&tsk->sighand->siglock);
if (!signal_group_exit(tsk->signal)) { if (!signal_group_exit(tsk->signal)) {
mm->core_state = core_state; mm->core_state = core_state;
nr = zap_process(tsk, exit_code);
tsk->signal->group_exit_task = tsk; tsk->signal->group_exit_task = tsk;
/* ignore all signals except SIGKILL, see prepare_signal() */ nr = zap_process(tsk, exit_code, 0);
tsk->signal->flags = SIGNAL_GROUP_COREDUMP;
clear_tsk_thread_flag(tsk, TIF_SIGPENDING); clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
} }
spin_unlock_irq(&tsk->sighand->siglock); spin_unlock_irq(&tsk->sighand->siglock);
@ -365,8 +365,8 @@ static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
if (p->mm) { if (p->mm) {
if (unlikely(p->mm == mm)) { if (unlikely(p->mm == mm)) {
lock_task_sighand(p, &flags); lock_task_sighand(p, &flags);
nr += zap_process(p, exit_code); nr += zap_process(p, exit_code,
p->signal->flags = SIGNAL_GROUP_EXIT; SIGNAL_GROUP_EXIT);
unlock_task_sighand(p, &flags); unlock_task_sighand(p, &flags);
} }
break; break;

2
kernel/signal.c
View File

@ -788,7 +788,7 @@ static bool prepare_signal(int sig, struct task_struct *p, bool force)
sigset_t flush; sigset_t flush;
if (signal->flags & (SIGNAL_GROUP_EXIT | SIGNAL_GROUP_COREDUMP)) { if (signal->flags & (SIGNAL_GROUP_EXIT | SIGNAL_GROUP_COREDUMP)) {
if (signal->flags & SIGNAL_GROUP_COREDUMP) if (!(signal->flags & SIGNAL_GROUP_EXIT))
return sig == SIGKILL; return sig == SIGKILL;
/* /*
* The process is in the middle of dying, nothing to do. * The process is in the middle of dying, nothing to do.