The patch titled
Subject: coredump: ensure all coredumping tasks have SIGNAL_GROUP_COREDUMP
has been added to the -mm tree. Its filename is
coredump-ensure-all-coredumping-tasks-have-signal_group_coredump.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/coredump-ensure-all-coredumping-tasks-have-signal_group_coredump.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/coredump-ensure-all-coredumping-tasks-have-signal_group_coredump.patch
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: coredump: ensure all coredumping tasks have SIGNAL_GROUP_COREDUMP
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@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Kyle Walker <kwalker@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Stanislav Kozina <skozina@xxxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/coredump.c | 12 ++++++------
kernel/signal.c | 2 +-
2 files changed, 7 insertions(+), 7 deletions(-)
diff -puN fs/coredump.c~coredump-ensure-all-coredumping-tasks-have-signal_group_coredump fs/coredump.c
--- a/fs/coredump.c~coredump-ensure-all-coredumping-tasks-have-signal_group_coredump
+++ a/fs/coredump.c
@@ -280,11 +280,13 @@ out:
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;
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_stop_count = 0;
@@ -311,10 +313,8 @@ static int zap_threads(struct task_struc
spin_lock_irq(&tsk->sighand->siglock);
if (!signal_group_exit(tsk->signal)) {
mm->core_state = core_state;
- nr = zap_process(tsk, exit_code);
tsk->signal->group_exit_task = tsk;
- /* ignore all signals except SIGKILL, see prepare_signal() */
- tsk->signal->flags = SIGNAL_GROUP_COREDUMP;
+ nr = zap_process(tsk, exit_code, 0);
clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
}
spin_unlock_irq(&tsk->sighand->siglock);
@@ -365,8 +365,8 @@ static int zap_threads(struct task_struc
if (p->mm) {
if (unlikely(p->mm == mm)) {
lock_task_sighand(p, &flags);
- nr += zap_process(p, exit_code);
- p->signal->flags = SIGNAL_GROUP_EXIT;
+ nr += zap_process(p, exit_code,
+ SIGNAL_GROUP_EXIT);
unlock_task_sighand(p, &flags);
}
break;
diff -puN kernel/signal.c~coredump-ensure-all-coredumping-tasks-have-signal_group_coredump kernel/signal.c
--- a/kernel/signal.c~coredump-ensure-all-coredumping-tasks-have-signal_group_coredump
+++ a/kernel/signal.c
@@ -788,7 +788,7 @@ static bool prepare_signal(int sig, stru
sigset_t flush;
if (signal->flags & (SIGNAL_GROUP_EXIT | SIGNAL_GROUP_COREDUMP)) {
- if (signal->flags & SIGNAL_GROUP_COREDUMP)
+ if (!(signal->flags & SIGNAL_GROUP_EXIT))
return sig == SIGKILL;
/*
* The process is in the middle of dying, nothing to do.
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
mm-fix-the-racy-mm-locked_vm-change-in.patch
mm-add-the-struct-mm_struct-mm-local-into.patch
signals-kill-block_all_signals-and-unblock_all_signals.patch
coredump-ensure-all-coredumping-tasks-have-signal_group_coredump.patch
coredump-change-zap_threads-and-zap_process-to-use.patch
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