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 000AB1E522; Thu, 30 Jan 2025 14:26:08 +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=1738247169; cv=none; b=NcOKlvx1EhCSLEt7UvaXu8xQlwSaTOcLu83GlqVotv97c7XbWF5Or3B9bLgqcobjmmhS6buSt3U6/uvUhyo/skGUwFbF4AcOYOYMQacuk5bUi2+tUeZ+3MsT9kVd0t8078XJ2Hc85N6Al0Kfk9vPgp5GMqFBztJha3ukjaseJOY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738247169; c=relaxed/simple; bh=mj05R9ycKLZelLZyEsf6zEL5CzECNq9HdDbKNiCcBaI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tXSmoirqRLn/TN935XGjqNVRpPzad4zgVNI8T3W1f+avVcKdQi5hOa/hnVIelgeM8ZXuJxUVJr6RbmnbKfVhqghhL42qutdO7BMrMFWhMTkTIwDH+Ios5PPyE+ZbZRR3/kM1gQVUFTJFaYLv41FTTjGL4QN2mo+7TvAyb74TvVk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=UINeGbOJ; 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="UINeGbOJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 767B5C4CEE0; Thu, 30 Jan 2025 14:26:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1738247168; bh=mj05R9ycKLZelLZyEsf6zEL5CzECNq9HdDbKNiCcBaI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UINeGbOJvx5SnMz/nUWbnifSiBP27F1U0XFedkBWIjilK4gtJKebEOjzAD43VnWCV 8o3PXe225tM5pSjG4LGGSdEP9gjGKUSx+gbLhbl80hntRdcmP+ITFtx14C8C4Dg0bd jAgmcUnZ048d6MvG+1rFtbubwtQ+jlJM3jS3EWso= 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 5.10 106/133] blk-cgroup: Fix UAF in blkcg_unpin_online() Date: Thu, 30 Jan 2025 15:01:35 +0100 Message-ID: <20250130140146.804744141@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250130140142.491490528@linuxfoundation.org> References: <20250130140142.491490528@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-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 @@ -428,10 +428,14 @@ 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); }