From: Peter Zijlstra <[email protected]> 3.12-stable review patch. If anyone has any objections, please let me know.
=============== commit e7cc4865f0f31698ef2f7aac01a50e78968985b7 upstream. While hunting for clues to a use-after-free, Oleg spotted that perf_event_init_context() can loose an error value with the result that fork() can succeed even though we did not fully inherit the perf event context. Spotted-by: Oleg Nesterov <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Alexander Shishkin <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Dmitry Vyukov <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Mathieu Desnoyers <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Stephane Eranian <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Vince Weaver <[email protected]> Cc: [email protected] Fixes: 889ff0150661 ("perf/core: Split context's event group list into pinned and non-pinned lists") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Jiri Slaby <[email protected]> --- kernel/events/core.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index a4a1516f3efc..0a360d3868c5 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7754,7 +7754,7 @@ int perf_event_init_context(struct task_struct *child, int ctxn) ret = inherit_task_group(event, parent, parent_ctx, child, ctxn, &inherited_all); if (ret) - break; + goto out_unlock; } /* @@ -7770,7 +7770,7 @@ int perf_event_init_context(struct task_struct *child, int ctxn) ret = inherit_task_group(event, parent, parent_ctx, child, ctxn, &inherited_all); if (ret) - break; + goto out_unlock; } raw_spin_lock_irqsave(&parent_ctx->lock, flags); @@ -7798,6 +7798,7 @@ int perf_event_init_context(struct task_struct *child, int ctxn) } raw_spin_unlock_irqrestore(&parent_ctx->lock, flags); +out_unlock: mutex_unlock(&parent_ctx->mutex); perf_unpin_context(parent_ctx); -- 2.12.2
