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 --- This is a backport of a DAMON fix that merged in the mainline, for v5.15.x stable series.

mm/damon/dbgfs.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c index f94d19a690df..d3bc110430f9 100644 --- a/mm/damon/dbgfs.c +++ b/mm/damon/dbgfs.c @@ -309,10 +309,12 @@ static int dbgfs_before_terminate(struct damon_ctx *ctx) 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; }