From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D1E85CCA487 for ; Thu, 21 Jul 2022 14:52:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232166AbiGUOwi (ORCPT ); Thu, 21 Jul 2022 10:52:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39166 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230451AbiGUOwh (ORCPT ); Thu, 21 Jul 2022 10:52:37 -0400 X-Greylist: delayed 327 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Thu, 21 Jul 2022 07:52:36 PDT Received: from box.fidei.email (box.fidei.email [71.19.144.250]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0FDAE27CD7; Thu, 21 Jul 2022 07:52:36 -0700 (PDT) Received: from authenticated-user (box.fidei.email [71.19.144.250]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits)) (No client certificate requested) by box.fidei.email (Postfix) with ESMTPSA id 19AB080AA3; Thu, 21 Jul 2022 10:47:06 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=dorminy.me; s=mail; t=1658414828; bh=ncqPM5vdKuFQDcqYet0UNkbdtGe6dSYkRKLHsgnTL8g=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=FLhI3SS2C01EXlMzqJwBDrVT4ydnt7LcBqFVGGxcIEbhAEJ6GQ1GYVyismRojqGPC k1L+Jg7/8OwUzohMK/1RfGgKhVZbTWh1e7XYPpWKjNG5mIH80K5ftcFu0JqQaFAuw6 pO2Zl/7BMnfQJ3IL7NDAyYZqgJ/hf2J/n/3at+S7bQHmfRz8hVakdZARt9ATgUU7/6 EdlzwU349IUuuBh/MaUpkuDT0tPRg/sYkIblVjCylEKcQ1lnLLcMpGWzB9jlT1My4d 7vf3EArzaDwb6rCW1DQ2BhKq2OMkfAlyK7rRkZhmir3w1zcShtxWDg6IZEgW71+r5a K+5LC6CSaC0aA== Message-ID: Date: Thu, 21 Jul 2022 10:47:05 -0400 MIME-Version: 1.0 Subject: Re: [PATCH] fs: btrfs: fix a possible use-after-free bug caused by incorrect error handling in prepare_to_relocate() Content-Language: en-US To: Zixuan Fu , clm@fb.com, josef@toxicpanda.com, dsterba@suse.com Cc: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, TOTE Robot References: <20220721074829.2905233-1-r33s3n6@gmail.com> From: Sweet Tea Dorminy In-Reply-To: <20220721074829.2905233-1-r33s3n6@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/21/22 03:48, Zixuan Fu wrote: > In btrfs_relocate_block_group(), the structure variable rc is allocated. > Then btrfs_relocate_block_group() calls relocate_block_group() -> > prepare_to_relocate() -> set_reloc_control(), and assigns rc to the > variable fs_info->reloc_ctl. When prepare_to_relocate() returns, it > calls btrfs_commit_transaction() -> btrfs_start_dirty_block_groups() > -> btrfs_alloc_path() -> kmem_cache_zalloc(), which may fail. When the > failure occurs, btrfs_relocate_block_group() detects the error and frees > rc and doesn't set fs_info->reloc_ctl to NULL. After that, in > btrfs_init_reloc_root(), rc is retrieved from fs_info->reloc_ctl and > then used, which may cause a use-after-free bug. > > This possible bug can be triggered by calling btrfs_ioctl_balance() > before calling btrfs_ioctl_defrag(). > > To fix this possible bug, in prepare_to_relocate(), an if statement > is added to check whether btrfs_commit_transaction() fails. If the > failure occurs, unset_reloc_control() is called to set > fs_info->reloc_ctl to NULL. > > The error log in our fault-injection testing is shown as follows: > > [ 58.751070] BUG: KASAN: use-after-free in btrfs_init_reloc_root+0x7ca/0x920 [btrfs] > ... > [ 58.753577] Call Trace: > ... > [ 58.755800] kasan_report+0x45/0x60 > [ 58.756066] btrfs_init_reloc_root+0x7ca/0x920 [btrfs] > [ 58.757304] record_root_in_trans+0x792/0xa10 [btrfs] > [ 58.757748] btrfs_record_root_in_trans+0x463/0x4f0 [btrfs] > [ 58.758231] start_transaction+0x896/0x2950 [btrfs] > [ 58.758661] btrfs_defrag_root+0x250/0xc00 [btrfs] > [ 58.759083] btrfs_ioctl_defrag+0x467/0xa00 [btrfs] > [ 58.759513] btrfs_ioctl+0x3c95/0x114e0 [btrfs] > ... > [ 58.768510] Allocated by task 23683: > [ 58.768777] ____kasan_kmalloc+0xb5/0xf0 > [ 58.769069] __kmalloc+0x227/0x3d0 > [ 58.769325] alloc_reloc_control+0x10a/0x3d0 [btrfs] > [ 58.769755] btrfs_relocate_block_group+0x7aa/0x1e20 [btrfs] > [ 58.770228] btrfs_relocate_chunk+0xf1/0x760 [btrfs] > [ 58.770655] __btrfs_balance+0x1326/0x1f10 [btrfs] > [ 58.771071] btrfs_balance+0x3150/0x3d30 [btrfs] > [ 58.771472] btrfs_ioctl_balance+0xd84/0x1410 [btrfs] > [ 58.771902] btrfs_ioctl+0x4caa/0x114e0 [btrfs] > ... > [ 58.773337] Freed by task 23683: > ... > [ 58.774815] kfree+0xda/0x2b0 > [ 58.775038] free_reloc_control+0x1d6/0x220 [btrfs] > [ 58.775465] btrfs_relocate_block_group+0x115c/0x1e20 [btrfs] > [ 58.775944] btrfs_relocate_chunk+0xf1/0x760 [btrfs] > [ 58.776369] __btrfs_balance+0x1326/0x1f10 [btrfs] > [ 58.776784] btrfs_balance+0x3150/0x3d30 [btrfs] > [ 58.777185] btrfs_ioctl_balance+0xd84/0x1410 [btrfs] > [ 58.777621] btrfs_ioctl+0x4caa/0x114e0 [btrfs] > ... > > Reported-by: TOTE Robot > Signed-off-by: Zixuan Fu Reviewed-by: Sweet Tea Dorminy > --- > fs/btrfs/relocation.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c > index a6dc827e75af..342ade83d062 100644 > --- a/fs/btrfs/relocation.c > +++ b/fs/btrfs/relocation.c > @@ -3573,7 +3573,12 @@ int prepare_to_relocate(struct reloc_control *rc) > */ > return PTR_ERR(trans); > } > - return btrfs_commit_transaction(trans); > + > + ret = btrfs_commit_transaction(trans); > + if (ret) > + unset_reloc_control(rc); > + > + return ret; > } > > static noinline_for_stack int relocate_block_group(struct reloc_control *rc)