From 69714a74c19f5ae8b21e25558d62d893d48a3f18 Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Sat, 17 Jan 2026 09:52:50 -0800 Subject: [PATCH] mm/damon/core: cancel damos_walk() before damon_ctx->kdamond reset damos_walk() request is canceled after damon_ctx->kdamond is reset. This can make weird situations where damon_is_running() returns false but the DAMON context has the damos_walk() request linked. There was a similar situation for damon_call() requests handling [1], which _was_ able to cause a racy use-after-free bug. Unlike the case of damon_call(), because damos_walk() is always synchronously handled and allows only single request at time, there is no such problematic race cases. But, keeping it as is could stem another subtle race condition bug in future. Avoid that by cancelling the requests before the ->kdamond reset. Note that this change also makes all damon_ctx dependent resource cleanups consistently done before the damon_ctx->kdamond reset. Link: https://lkml.kernel.org/r/20260117175256.82826-4-sj@kernel.org Link: https://lore.kernel.org/20251230014532.47563-1-sj@kernel.org [1] Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton --- mm/damon/core.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 0c8ac11a49f92..0bed937b1dcec 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2856,14 +2856,13 @@ done: kfree(ctx->regions_score_histogram); kdamond_call(ctx, true); + damos_walk_cancel(ctx); pr_debug("kdamond (%d) finishes\n", current->pid); mutex_lock(&ctx->kdamond_lock); ctx->kdamond = NULL; mutex_unlock(&ctx->kdamond_lock); - damos_walk_cancel(ctx); - mutex_lock(&damon_lock); nr_running_ctxs--; if (!nr_running_ctxs && running_exclusive_ctxs) -- 2.47.3