4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Vinayak Menon <vinme...@codeaurora.org>
[ Upstream commit 914b6dfff790544d9b77dfd1723adb3745ec9700 ]
A crash is observed when kmemleak_scan accesses the object->pointer,
likely due to the following race.
TASK A TASK B TASK C
kmemleak_write
(with "scan" and
NOT "scan=on")
kmemleak_scan()
create_object
kmem_cache_alloc fails
kmemleak_disable
kmemleak_do_cleanup
kmemleak_free_enabled = 0
kfree
kmemleak_free bails out
(kmemleak_free_enabled is 0)
slub frees object->pointer
update_checksum
crash - object->pointer
freed (DEBUG_PAGEALLOC)
kmemleak_do_cleanup waits for the scan thread to complete, but not for
direct call to kmemleak_scan via kmemleak_write. So add a wait for
kmemleak_scan completion before disabling kmemleak_free, and while at it
fix the comment on stop_scan_thread.
[vinme...@codeaurora.org: fix stop_scan_thread comment]
Link:
http://lkml.kernel.org/r/1522219972-22809-1-git-send-email-vinme...@codeaurora.org
Link:
http://lkml.kernel.org/r/1522063429-18992-1-git-send-email-vinme...@codeaurora.org
Signed-off-by: Vinayak Menon <vinme...@codeaurora.org>
Reviewed-by: Catalin Marinas <catalin.mari...@arm.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
mm/kmemleak.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1658,8 +1658,7 @@ static void start_scan_thread(void)
}
/*
- * Stop the automatic memory scanning thread. This function must be called
- * with the scan_mutex held.
+ * Stop the automatic memory scanning thread.
*/
static void stop_scan_thread(void)
{
@@ -1922,12 +1921,15 @@ static void kmemleak_do_cleanup(struct w
{
stop_scan_thread();
+ mutex_lock(&scan_mutex);
/*
- * Once the scan thread has stopped, it is safe to no longer track
- * object freeing. Ordering of the scan thread stopping and the memory
- * accesses below is guaranteed by the kthread_stop() function.
+ * Once it is made sure that kmemleak_scan has stopped, it is safe to no
+ * longer track object freeing. Ordering of the scan thread stopping and
+ * the memory accesses below is guaranteed by the kthread_stop()
+ * function.
*/
kmemleak_free_enabled = 0;
+ mutex_unlock(&scan_mutex);
if (!kmemleak_found_leaks)
__kmemleak_do_cleanup();
