From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F02B435AC1B; Thu, 2 Apr 2026 18:17:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775153854; cv=none; b=IVgaftVJDkoU9JUB77BKqk/Kc3NqkjDWWmLHHh1swHRiYBPtrC9kaeCtzo0LllhOKR/sYJOMzPs0bHASW/EqMjz5FuKez+AXsNyNP5smufa1Q6V0+GuEPYaorDqK9sReV+D6SyaHhpQpm7StXo6L1yB39kyeApEYXbEzZ5k15Jo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775153854; c=relaxed/simple; bh=k1j5trEatp42J/GAwpkXQBO8emp69M+cIR1Do9O1ZUE=; h=Date:To:From:Subject:Message-Id; b=saHFVmxzGOUddi75fhUKEgZZlskJKgIms9GOQMlOGzW15FK4jfCWK3iDA3HmUNlCbkQAv7Ab5DBR9DZ4c2z3JQrIl7AiLKY6JOcpgE3uol/ISpXOZSX/HhCKERU3MFzWVurPvFc5k4JtK9Q7z9WsQEYnicKmIjkpgAgiFnQkBuA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=0F6WEl41; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="0F6WEl41" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 91380C116C6; Thu, 2 Apr 2026 18:17:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1775153853; bh=k1j5trEatp42J/GAwpkXQBO8emp69M+cIR1Do9O1ZUE=; h=Date:To:From:Subject:From; b=0F6WEl41kitUOHdN3Dk0jEKvIBlaEfuPcDTF2JW45ICBWmaM2BmT+1xfkS6jVVClM nR9Ys7UFkeBJrE0OK8+Jw9Kmbm1XK+w+VSkZYg4CnQ7qGp3D+roTWJAbw2vEHchsAz fK+t2hF5eljb8s52HGMuVUhRpPeNFHPOT9RJl2b4= Date: Thu, 02 Apr 2026 11:17:32 -0700 To: mm-commits@vger.kernel.org,stable@vger.kernel.org,sj@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-damon-stat-deallocate-damon_call-failure-leaking-damon_ctx.patch added to mm-hotfixes-unstable branch Message-Id: <20260402181733.91380C116C6@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/damon/stat: deallocate damon_call() failure leaking damon_ctx has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-damon-stat-deallocate-damon_call-failure-leaking-damon_ctx.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-stat-deallocate-damon_call-failure-leaking-damon_ctx.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: SeongJae Park Subject: mm/damon/stat: deallocate damon_call() failure leaking damon_ctx Date: Thu, 2 Apr 2026 06:44:17 -0700 damon_stat_start() always allocates the module's damon_ctx object (damon_stat_context). Meanwhile, if damon_call() in the function fails, the damon_ctx object is not deallocated. Hence, if the damon_call() is failed, and the user writes Y to “enabled” again, the previously allocated damon_ctx object is leaked. This cannot simply be fixed by deallocating the damon_ctx object when damon_call() fails. That's because damon_call() failure doesn't guarantee the kdamond main function, which accesses the damon_ctx object, is completely finished. In other words, if damon_stat_start() deallocates the damon_ctx object after damon_call() failure, the not-yet-terminated kdamond could access the freed memory (use-after-free). Fix the leak while avoiding the use-after-free by keeping returning damon_stat_start() without deallocating the damon_ctx object after damon_call() failure, but deallocating it when the function is invoked again and the kdamond is completely terminated. If the kdamond is not yet terminated, simply return -EAGAIN, as the kdamond will soon be terminated. The issue was discovered [1] by sashiko. Link: https://lkml.kernel.org/r/20260402134418.74121-1-sj@kernel.org Link: https://lore.kernel.org/20260401012428.86694-1-sj@kernel.org [1] Fixes: 405f61996d9d ("mm/damon/stat: use damon_call() repeat mode instead of damon_callback") Signed-off-by: SeongJae Park Cc: # 6.17.x Signed-off-by: Andrew Morton --- mm/damon/stat.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/mm/damon/stat.c~mm-damon-stat-deallocate-damon_call-failure-leaking-damon_ctx +++ a/mm/damon/stat.c @@ -245,6 +245,12 @@ static int damon_stat_start(void) { int err; + if (damon_stat_context) { + if (damon_is_running(damon_stat_context)) + return -EAGAIN; + damon_destroy_ctx(damon_stat_context); + } + damon_stat_context = damon_stat_build_ctx(); if (!damon_stat_context) return -ENOMEM; @@ -261,6 +267,7 @@ static void damon_stat_stop(void) { damon_stop(&damon_stat_context, 1); damon_destroy_ctx(damon_stat_context); + damon_stat_context = NULL; } static int damon_stat_enabled_store( _ Patches currently in -mm which might be from sj@kernel.org are mm-damon-sysfs-dealloc-repeat_call_control-if-damon_call-fails.patch mm-damon-stat-deallocate-damon_call-failure-leaking-damon_ctx.patch mm-damon-core-fix-damon_call-vs-kdamond_fn-exit-race.patch mm-damon-core-fix-damos_walk-vs-kdamond_fn-exit-race.patch mm-damon-core-validate-damos_quota_goal-nid-for-node_mem_usedfree_bp.patch mm-damon-core-validate-damos_quota_goal-nid-for-node_memcg_usedfree_bp.patch mm-damon-core-use-time_in_range_open-for-damos-quota-window-start.patch docs-admin-guide-mm-damon-reclaim-warn-commit_inputs-vs-param-updates-race.patch docs-admin-guide-mm-damon-lru_sort-warn-commit_inputs-vs-param-updates-race.patch