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. [1] https://lore.kernel.org/20251230014532.47563-1-sj@kernel.org Signed-off-by: SeongJae Park --- 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 0c8ac11a49f9..0bed937b1dce 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2856,14 +2856,13 @@ static int kdamond_fn(void *data) 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