From 05cbaa2853cdfc255fdd04e65a82bfe9208c4e52 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 30 Dec 2009 16:00:35 +0100 Subject: [PATCH] perf: Fix NULL deref in inheritance code Liming found a NULL deref when a task has a perf context but no counters when it forks. This can occur in two cases, a race during construction where the fork hits after installing the context but before the first counter gets inserted, or more reproducably, a fork after the last counter is closed (which leaves the context around). Reported-by: Wang Liming Signed-off-by: Peter Zijlstra Cc: Frederic Weisbecker Cc: Paul Mackerras CC: LKML-Reference: <1262185684.7135.222.camel@laptop> Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 03cc061398d1..58ed1dae5875 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -5148,7 +5148,7 @@ int perf_event_init_task(struct task_struct *child) GFP_KERNEL); if (!child_ctx) { ret = -ENOMEM; - goto exit; + break; } __perf_event_init_context(child_ctx, child); @@ -5164,7 +5164,7 @@ int perf_event_init_task(struct task_struct *child) } } - if (inherited_all) { + if (child_ctx && inherited_all) { /* * Mark the child context as a clone of the parent * context, or of whatever the parent is a clone of. @@ -5184,7 +5184,6 @@ int perf_event_init_task(struct task_struct *child) get_ctx(child_ctx->parent_ctx); } -exit: mutex_unlock(&parent_ctx->mutex); perf_unpin_context(parent_ctx);