3.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Peter Zijlstra <pet...@infradead.org>
commit 6c72e3501d0d62fc064d3680e5234f3463ec5a86 upstream.
Oleg noticed that a cleanup by Sylvain actually uncovered a bug; by
calling perf_event_free_task() when failing sched_fork() we will not yet
have done the memset() on ->perf_event_ctxp[] and will therefore try and
'free' the inherited contexts, which are still in use by the parent
process. This is bad..
Suggested-by: Oleg Nesterov <o...@redhat.com>
Reported-by: Oleg Nesterov <o...@redhat.com>
Reported-by: Sylvain 'ythier' Hitier <sylvain.hit...@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
kernel/events/core.c | 4 +++-
kernel/fork.c | 5 +++--
2 files changed, 6 insertions(+), 3 deletions(-)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7921,8 +7921,10 @@ int perf_event_init_task(struct task_str
for_each_task_context_nr(ctxn) {
ret = perf_event_init_context(child, ctxn);
- if (ret)
+ if (ret) {
+ perf_event_free_task(child);
return ret;
+ }
}
return 0;
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1326,7 +1326,7 @@ static struct task_struct *copy_process(
goto bad_fork_cleanup_policy;
retval = audit_alloc(p);
if (retval)
- goto bad_fork_cleanup_policy;
+ goto bad_fork_cleanup_perf;
/* copy all the process information */
retval = copy_semundo(clone_flags, p);
if (retval)
@@ -1525,8 +1525,9 @@ bad_fork_cleanup_semundo:
exit_sem(p);
bad_fork_cleanup_audit:
audit_free(p);
-bad_fork_cleanup_policy:
+bad_fork_cleanup_perf:
perf_event_free_task(p);
+bad_fork_cleanup_policy:
#ifdef CONFIG_NUMA
mpol_put(p->mempolicy);
bad_fork_cleanup_threadgroup_lock:
--
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