[PATCH 5.15 105/128] mm/damon/dbgfs: protect targets destructions with kdamond_lock

Greg Kroah-Hartman
2021-12-27T15:48:14Z

From: SeongJae Park <sj@kernel.org>

commit 34796417964b8d0aef45a99cf6c2d20cebe33733 upstream.

DAMON debugfs interface iterates current monitoring targets in
'dbgfs_target_ids_read()' while holding the corresponding
'kdamond_lock'. However, it also destructs the monitoring targets in
'dbgfs_before_terminate()' without holding the lock. This can result in
a use_after_free bug. This commit avoids the race by protecting the
destruction with the corresponding 'kdamond_lock'.

Link: https://lkml.kernel.org/r/20211221094447.2241-1-sj@kernel.org
Reported-by: Sangwoo Bae <sangwoob@amazon.com>
Fixes: 4bc05954d007 ("mm/damon: implement a debugfs-based user space interface")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> [5.15.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/damon/dbgfs.c | 2 ++
1 file changed, 2 insertions(+)

--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -309,10 +309,12 @@ static int dbgfs_before_terminate(struct
if (!targetid_is_pid(ctx))
return 0;

+ mutex_lock(&ctx->kdamond_lock);
damon_for_each_target_safe(t, next, ctx) {
put_pid((struct pid *)t->id);
damon_destroy_target(t);
}
+ mutex_unlock(&ctx->kdamond_lock);
return 0;
}