From: SeongJae Park <sj@xxxxxxxxxx> 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@xxxxxxxxxx Reported-by: Sangwoo Bae <sangwoob@xxxxxxxxxx> Fixes: 4bc05954d007 ("mm/damon: implement a debugfs-based user space interface") Signed-off-by: SeongJae Park <sj@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [5.15.x] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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; }
