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 A9CBC4C80 for ; Sun, 15 Dec 2024 07:41:51 +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=1734248511; cv=none; b=Ba6JQqLxK1EyKBJqlRPsQk8HBYYwnhgyRaZmdYtSRAocA62/cUT8/gkkLC+ndGctbEdeS1Qpf1UogCPj4ao/2Jh3QjRVv58bkCyjkYD4ssWDynagjwecN13ygyyHwWkTEMNodoumdfU6fApFdFgOVZxI+PQOO9d1n8M1NwYsiaU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734248511; c=relaxed/simple; bh=Q4cNc+MNvGy0jeQwYvpJS8j6pI+nRozuEJxpTjqbbS8=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=rnrFDoRQ1erCdYLkXs9xaKzn7tNXCw06ulFH2zJT5wKi7LaaXQXbEwJV/VhynBVR1Tcv/7edDIFoeB5GU2oc59QTx7ob9LAMJiEfknTNoXYcXirvImBhTTBc1fBrlVdCcakv2+99HVbpXxCWTRgRBbYEnxgPzdAZ/KJmMeO6Ws8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=aDkUgxQi; 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="aDkUgxQi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1E9EC4CECE; Sun, 15 Dec 2024 07:41:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1734248511; bh=Q4cNc+MNvGy0jeQwYvpJS8j6pI+nRozuEJxpTjqbbS8=; h=Subject:To:Cc:From:Date:From; b=aDkUgxQiJKDhGm+OyNkW8zBeBg7IsmkoKM+KdTVnq/gridICPWVl6zQpqoi/JzqK0 Jv+rhtxywthwZ1nYC6o8CEov3slx+kpNYVkNy/rDUAviiJrLdqU2vemACk8WL8UJzB 9gTRqiby3VJgj6KINePXNS4holVCoug/ZNuj9YlY= Subject: FAILED: patch "[PATCH] blk-cgroup: Fix UAF in blkcg_unpin_online()" failed to apply to 5.10-stable tree To: tj@kernel.org,axboe@kernel.dk,renzezhongucas@gmail.com,torvalds@linuxfoundation.org Cc: From: Date: Sun, 15 Dec 2024 08:41:39 +0100 Message-ID: <2024121539-nutty-gangly-3dff@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 5.10-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-5.10.y git checkout FETCH_HEAD git cherry-pick -x 86e6ca55b83c575ab0f2e105cf08f98e58d3d7af # git commit -s git send-email --to '' --in-reply-to '2024121539-nutty-gangly-3dff@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 86e6ca55b83c575ab0f2e105cf08f98e58d3d7af Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 6 Dec 2024 07:59:51 -1000 Subject: [PATCH] blk-cgroup: Fix UAF in blkcg_unpin_online() blkcg_unpin_online() walks up the blkcg hierarchy putting the online pin. To walk up, it uses blkcg_parent(blkcg) but it was calling that after blkcg_destroy_blkgs(blkcg) which could free the blkcg, leading to the following UAF: ================================================================== BUG: KASAN: slab-use-after-free in blkcg_unpin_online+0x15a/0x270 Read of size 8 at addr ffff8881057678c0 by task kworker/9:1/117 CPU: 9 UID: 0 PID: 117 Comm: kworker/9:1 Not tainted 6.13.0-rc1-work-00182-gb8f52214c61a-dirty #48 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS unknown 02/02/2022 Workqueue: cgwb_release cgwb_release_workfn Call Trace: dump_stack_lvl+0x27/0x80 print_report+0x151/0x710 kasan_report+0xc0/0x100 blkcg_unpin_online+0x15a/0x270 cgwb_release_workfn+0x194/0x480 process_scheduled_works+0x71b/0xe20 worker_thread+0x82a/0xbd0 kthread+0x242/0x2c0 ret_from_fork+0x33/0x70 ret_from_fork_asm+0x1a/0x30 ... Freed by task 1944: kasan_save_track+0x2b/0x70 kasan_save_free_info+0x3c/0x50 __kasan_slab_free+0x33/0x50 kfree+0x10c/0x330 css_free_rwork_fn+0xe6/0xb30 process_scheduled_works+0x71b/0xe20 worker_thread+0x82a/0xbd0 kthread+0x242/0x2c0 ret_from_fork+0x33/0x70 ret_from_fork_asm+0x1a/0x30 Note that the UAF is not easy to trigger as the free path is indirected behind a couple RCU grace periods and a work item execution. I could only trigger it with artifical msleep() injected in blkcg_unpin_online(). Fix it by reading the parent pointer before destroying the blkcg's blkg's. Signed-off-by: Tejun Heo Reported-by: Abagail ren Suggested-by: Linus Torvalds Fixes: 4308a434e5e0 ("blkcg: don't offline parent blkcg first") Cc: stable@vger.kernel.org # v5.7+ Signed-off-by: Jens Axboe diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index e68c725cf8d9..45a395862fbc 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1324,10 +1324,14 @@ void blkcg_unpin_online(struct cgroup_subsys_state *blkcg_css) struct blkcg *blkcg = css_to_blkcg(blkcg_css); do { + struct blkcg *parent; + if (!refcount_dec_and_test(&blkcg->online_pin)) break; + + parent = blkcg_parent(blkcg); blkcg_destroy_blkgs(blkcg); - blkcg = blkcg_parent(blkcg); + blkcg = parent; } while (blkcg); }