Commit-ID: ebf905fc7a6e7c99c53b5afc888d8f950da90aff
Gitweb: http://git.kernel.org/tip/ebf905fc7a6e7c99c53b5afc888d8f950da90aff
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Thu, 29 May 2014 19:00:24 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 5 Jun 2014 12:29:52 +0200
perf: Fix use after free in perf_remove_from_context()
While that mutex should guard the elements, it doesn't guard against the
use-after-free that's from list_for_each_entry_rcu().
__perf_event_exit_task() can actually free the event.
And because list addition/deletion is guarded by both ctx->mutex and
ctx->lock, holding ctx->mutex is sufficient for reading the list, so we
don't actually need the rcu list iteration.
Fixes: 3a497f48637e ("perf: Simplify perf_event_exit_task_context()")
Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
Tested-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Dave Jones <davej@xxxxxxxxxx>
Cc: acme@xxxxxxxxxxxxxxxxxx
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20140529170024.GA2315@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/events/core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index ed50b09..a62d142 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7431,7 +7431,7 @@ __perf_event_exit_task(struct perf_event *child_event,
static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
{
- struct perf_event *child_event;
+ struct perf_event *child_event, *next;
struct perf_event_context *child_ctx;
unsigned long flags;
@@ -7485,7 +7485,7 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
*/
mutex_lock(&child_ctx->mutex);
- list_for_each_entry_rcu(child_event, &child_ctx->event_list, event_entry)
+ list_for_each_entry_safe(child_event, next, &child_ctx->event_list, event_entry)
__perf_event_exit_task(child_event, child_ctx, child);
mutex_unlock(&child_ctx->mutex);
--
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