From patchwork Wed Jan 15 09:37:09 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vasiliy Kovalev X-Patchwork-Id: 13940162 Received: from air.basealt.ru (air.basealt.ru [193.43.8.18]) (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 6DA29248164; Wed, 15 Jan 2025 09:37:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.43.8.18 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736933845; cv=none; b=B4W7eFZyxwLL+yXMlaCM9N+xD6yV7hZ3WmfD5HulTiZ89+u9BcZIs4wq/6acduasPI8UuAd+KgH0eH3dp6c2BWBeWfCR2F1ThYJZeMLV8Znt5a/NCfstoknv+Yw/V7ulMWIpe7sCtz31VWPBdtRx/UlQKwOQGn5/8fYze3smsPc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736933845; c=relaxed/simple; bh=RICQ+FugO2UuAfARIMKAug4IAivXM59w3ZjanIHQpkc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=iN0lfQrPRcc5XY0NCOehem8tyDZi7ZKinHkDAMb9VL///AddYGNw/mGq7dXm2ZABqV7jYCy9nfqfxOKos5UlDO69WwmO9C+n6RkOnvxT0Sc5M0xX0IQeyYJNHygJLTubbbDH4RTUMybEgl7FrTMIPw5s42vvX7nLjBooIQjqkFo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=altlinux.org; spf=pass smtp.mailfrom=altlinux.org; arc=none smtp.client-ip=193.43.8.18 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=altlinux.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=altlinux.org Received: from altlinux.ipa.basealt.ru (unknown [178.76.204.78]) by air.basealt.ru (Postfix) with ESMTPSA id 3B720233A9; Wed, 15 Jan 2025 12:37:20 +0300 (MSK) From: Vasiliy Kovalev To: stable@vger.kernel.org Cc: linux-block@vger.kernel.org, cgroups@vger.kernel.org, lvc-project@linuxtesting.org, kovalev@altlinux.org, Tejun Heo , Abagail ren , Linus Torvalds , Jens Axboe Subject: [PATCH 5.10/5.15] blk-cgroup: Fix UAF in blkcg_unpin_online() Date: Wed, 15 Jan 2025 12:37:09 +0300 Message-Id: <20250115093709.335950-1-kovalev@altlinux.org> X-Mailer: git-send-email 2.33.8 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Tejun Heo commit 86e6ca55b83c575ab0f2e105cf08f98e58d3d7af upstream. 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 [kovalev: in versions 5.10 and 5.15, the blkcg_unpin_online() function was not moved to the block/blk-cgroup.c file] Signed-off-by: Vasiliy Kovalev --- Backport to fix CVE-2024-56672 Link: https://www.cve.org/CVERecord/?id=CVE-2024-56672 --- include/linux/blk-cgroup.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h index 0e6e84db06f674..b89099360a8673 100644 --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -428,10 +428,14 @@ static inline void blkcg_pin_online(struct blkcg *blkcg) static inline void blkcg_unpin_online(struct blkcg *blkcg) { 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); }