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 6FD113815F2 for ; Mon, 30 Mar 2026 09:52:36 +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=1774864356; cv=none; b=UWc9+LVPNP4TgILhIWZVp44X8YghCwq8hZk233xVQujhoqvXYKbbbdFQzO+OSLa1ffabcn4d2hQcbY1zLdgqmk9OxPvYAPxHLE3dBAnz0KwxIGjw9eW+Wqcn9TbSBt97ZQmILvu+K7MaeTzwaVSU98Qb4PjXSK+VdcWVctMRxNk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774864356; c=relaxed/simple; bh=gCda9YsZIyDH8fpUbCcDQsnC0Uqjl5kDnZV6hkO5+iM=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=PR7gzZ/eJeTg7jCDS1sI883fRjF8xAT8ANvb33ZiSgLmvXATiylXwdPhSEgIsjB2/dcFxn76HE0Gl5uQoIJgOV4wwBwLn8Or6N5Ewp92aBaJDUPoap5AxN0NEAR/DiCMS0FfaSp4UTlQwpuhCh3EN2M2FQcL/W0jSzHwiNZ5jxc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JQUAe7NW; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="JQUAe7NW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D60BFC2BC9E; Mon, 30 Mar 2026 09:52:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774864356; bh=gCda9YsZIyDH8fpUbCcDQsnC0Uqjl5kDnZV6hkO5+iM=; h=Subject:To:Cc:From:Date:From; b=JQUAe7NWpv2PI95ZL25Fg3Fn2vVvK30crAxeksvxP51BNaTx2a6XSsHPOcPBycZRE J5tWum3wIWFODhbCfRAYjoz5SURqRriR2S9RVpDP1J8qPL/2hn+BV7ynpwZ5G2ZSsz gBlhDw3ROFnY2mP2ApUJ0n/yZc+nRa9LCwQT+npI= Subject: FAILED: patch "[PATCH] mm/damon/sysfs: check contexts->nr before accessing" failed to apply to 6.12-stable tree To: objecting@objecting.org,akpm@linux-foundation.org,sj@kernel.org,stable@vger.kernel.org Cc: From: Date: Mon, 30 Mar 2026 11:52:32 +0200 Message-ID: <2026033032-savor-relearn-225e@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 1bfe9fb5ed2667fb075682408b776b5273162615 # git commit -s git send-email --to '' --in-reply-to '2026033032-savor-relearn-225e@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 1bfe9fb5ed2667fb075682408b776b5273162615 Mon Sep 17 00:00:00 2001 From: Josh Law Date: Sat, 21 Mar 2026 10:54:25 -0700 Subject: [PATCH] mm/damon/sysfs: check contexts->nr before accessing contexts_arr[0] Multiple sysfs command paths dereference contexts_arr[0] without first verifying that kdamond->contexts->nr == 1. A user can set nr_contexts to 0 via sysfs while DAMON is running, causing NULL pointer dereferences. In more detail, the issue can be triggered by privileged users like below. First, start DAMON and make contexts directory empty (kdamond->contexts->nr == 0). # damo start # cd /sys/kernel/mm/damon/admin/kdamonds/0 # echo 0 > contexts/nr_contexts Then, each of below commands will cause the NULL pointer dereference. # echo update_schemes_stats > state # echo update_schemes_tried_regions > state # echo update_schemes_tried_bytes > state # echo update_schemes_effective_quotas > state # echo update_tuned_intervals > state Guard all commands (except OFF) at the entry point of damon_sysfs_handle_cmd(). Link: https://lkml.kernel.org/r/20260321175427.86000-3-sj@kernel.org Fixes: 0ac32b8affb5 ("mm/damon/sysfs: support DAMOS stats") Signed-off-by: Josh Law Reviewed-by: SeongJae Park Signed-off-by: SeongJae Park Cc: [5.18+] Signed-off-by: Andrew Morton diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c index b573b9d60784..ddc30586c0e6 100644 --- a/mm/damon/sysfs.c +++ b/mm/damon/sysfs.c @@ -1749,6 +1749,9 @@ static int damon_sysfs_update_schemes_tried_regions( static int damon_sysfs_handle_cmd(enum damon_sysfs_cmd cmd, struct damon_sysfs_kdamond *kdamond) { + if (cmd != DAMON_SYSFS_CMD_OFF && kdamond->contexts->nr != 1) + return -EINVAL; + switch (cmd) { case DAMON_SYSFS_CMD_ON: return damon_sysfs_turn_damon_on(kdamond);