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Subject[PATCH 3/3] 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>
---
fs/coredump.c | 12 +++++++-----
1 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index 835d731..5503d94 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -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,
@@ -632,9 +635,8 @@ 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);
@@ -647,7 +649,7 @@ 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);
--
1.5.5.1


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