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 627981F7080; Tue, 21 Jan 2025 18:11:56 +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=1737483116; cv=none; b=O7VgmlBwy053IeJZxbbBAS0SY+k+YLRVFYPVsDqD5kUlF4raa171eRw55U6dN4lpxD/vVa2aDjJ98vdFm6ymqC0yaZJblHlMvTOd14zxeygZpgJOJB3rQ6z/7Ar8kt2N0Qsk6klEjlpAE7puEKX2SBfc1EnTFZfiKUGfRdyQzZM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737483116; c=relaxed/simple; bh=YYnyDiCZTRQmj0n3swrKHqVrz1IGa4HECNNloZjql9Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ovyIjga8S1fiM6SkfmzJ4t1NnSIXzhuOw28h3wWQZM/va5e5YJKbY6nT0CjpcXTVpgqxDa8703kxFEQdJ+tScV7urYu5/1z/OoiAvpNO+sKgOQSKId9HyiVWE3hzAur5N27puGt/kYKUOrFK+vWXBHh/EHcJoQNw6pGSkrwPob0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ulmvuJhg; 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="ulmvuJhg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DF294C4CEDF; Tue, 21 Jan 2025 18:11:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1737483116; bh=YYnyDiCZTRQmj0n3swrKHqVrz1IGa4HECNNloZjql9Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ulmvuJhge4bRTa3HPRqYYaoDzFS8XdgRlrAN2AGoau4DMSUne7U7fJJwHRGUSR8oX PYAopXUKcLXSt7o3bO+vGLk1Zt2moqIb409vg4ORHnYpa4D9YbszUBMqU4I37nXLU4 C+CY4osiuM+p4W0LyFyoiEktPaqiIFHm0HabGM34= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tejun Heo , Abagail ren , Linus Torvalds , Jens Axboe Subject: [PATCH 5.15 121/127] blk-cgroup: Fix UAF in blkcg_unpin_online() Date: Tue, 21 Jan 2025 18:53:13 +0100 Message-ID: <20250121174534.303943517@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250121174529.674452028@linuxfoundation.org> References: <20250121174529.674452028@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ 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 Signed-off-by: Greg Kroah-Hartman --- include/linux/blk-cgroup.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -433,10 +433,14 @@ static inline void blkcg_pin_online(stru 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); }