From: SeongJae Park sj@kernel.org Subject: mm/damon/dbgfs: protect targets destructions with kdamond_lock

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 ---

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

--- a/mm/damon/dbgfs.c~mm-damon-dbgfs-protect-targets-destructions-with-kdamond_lock +++ a/mm/damon/dbgfs.c @@ -650,10 +650,12 @@ static void dbgfs_before_terminate(struc if (!targetid_is_pid(ctx)) return;

+ 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); }

static struct damon_ctx *dbgfs_new_ctx(void) _