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 034031DF272; Wed, 6 Nov 2024 12:18:58 +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=1730895538; cv=none; b=UcrsWbeSuFVVFJUFE+w5fR/Gf72ulfhF4BUIqHd9ULqf9ON3WQpvF+oTP8+C+qbusQceJD7mPdaAHueMcShE/Ae3vkmoSLZhLBkG/4/tbYeM37U1tGnDSk6Ert6ly+RyuClXuCYScJx5iDqknwmuwhhiKNVBULHKn1Z3Dr/X7nA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730895538; c=relaxed/simple; bh=/7USTIEnU/YBsMOKLj1EQqWtOZqIRZTaRk+w4XWu2II=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZLEY3QasTh4ESeitPaTdFNQpwY6lG5gOiDEWWRN5083hy94Guss6U/i9qdS9c0wv8GZ1tdTJBIpBykSA2zR3NCeKsi/wFV+OG7Y7SHh9+lYYFA4c4b5rn6oHgK1W5u8/6PV9GP2L3nztIrIEBJcGUROydxHI0HtJmAO307H+MKk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qbjT5lag; 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="qbjT5lag" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7C7DEC4CECD; Wed, 6 Nov 2024 12:18:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1730895537; bh=/7USTIEnU/YBsMOKLj1EQqWtOZqIRZTaRk+w4XWu2II=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qbjT5lagLht1SQ3G4PRCAabmNvpFplZjTSWGfolUrgcwfd+zV//k8UsaLwH+6GjOT wEPuIE76Mt2tvsynpgm2UIjslHMRSH7SLUnVWISrNfpdFeLq4+7Kmfqma+fbzEpOB0 i5uo6Mhhdvk0DOZshxlYYDLJlNaD7Ne7MRSFf+EY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable@kernel.org, Baokun Li , Jan Kara , Ojaswin Mujoo , Theodore Tso , Sasha Levin Subject: [PATCH 4.19 215/350] ext4: fix slab-use-after-free in ext4_split_extent_at() Date: Wed, 6 Nov 2024 13:02:23 +0100 Message-ID: <20241106120326.309386885@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241106120320.865793091@linuxfoundation.org> References: <20241106120320.865793091@linuxfoundation.org> User-Agent: quilt/0.67 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 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Baokun Li [ Upstream commit c26ab35702f8cd0cdc78f96aa5856bfb77be798f ] We hit the following use-after-free: ================================================================== BUG: KASAN: slab-use-after-free in ext4_split_extent_at+0xba8/0xcc0 Read of size 2 at addr ffff88810548ed08 by task kworker/u20:0/40 CPU: 0 PID: 40 Comm: kworker/u20:0 Not tainted 6.9.0-dirty #724 Call Trace: kasan_report+0x93/0xc0 ext4_split_extent_at+0xba8/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Allocated by task 40: __kmalloc_noprof+0x1ac/0x480 ext4_find_extent+0xf3b/0x1e70 ext4_ext_map_blocks+0x188/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Freed by task 40: kfree+0xf1/0x2b0 ext4_find_extent+0xa71/0x1e70 ext4_ext_insert_extent+0xa22/0x3260 ext4_split_extent_at+0x3ef/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ================================================================== The flow of issue triggering is as follows: ext4_split_extent_at path = *ppath ext4_ext_insert_extent(ppath) ext4_ext_create_new_leaf(ppath) ext4_find_extent(orig_path) path = *orig_path read_extent_tree_block // return -ENOMEM or -EIO ext4_free_ext_path(path) kfree(path) *orig_path = NULL a. If err is -ENOMEM: ext4_ext_dirty(path + path->p_depth) // path use-after-free !!! b. If err is -EIO and we have EXT_DEBUG defined: ext4_ext_show_leaf(path) eh = path[depth].p_hdr // path also use-after-free !!! So when trying to zeroout or fix the extent length, call ext4_find_extent() to update the path. In addition we use *ppath directly as an ext4_ext_show_leaf() input to avoid possible use-after-free when EXT_DEBUG is defined, and to avoid unnecessary path updates. Fixes: dfe5080939ea ("ext4: drop EXT4_EX_NOFREE_ON_ERR from rest of extents handling code") Cc: stable@kernel.org Signed-off-by: Baokun Li Reviewed-by: Jan Kara Reviewed-by: Ojaswin Mujoo Tested-by: Ojaswin Mujoo Link: https://patch.msgid.link/20240822023545.1994557-4-libaokun@huaweicloud.com Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- fs/ext4/extents.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 080a7a401a4e1..c538d09542391 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3294,6 +3294,25 @@ static int ext4_split_extent_at(handle_t *handle, if (err != -ENOSPC && err != -EDQUOT) goto out; + /* + * Update path is required because previous ext4_ext_insert_extent() + * may have freed or reallocated the path. Using EXT4_EX_NOFAIL + * guarantees that ext4_find_extent() will not return -ENOMEM, + * otherwise -ENOMEM will cause a retry in do_writepages(), and a + * WARN_ON may be triggered in ext4_da_update_reserve_space() due to + * an incorrect ee_len causing the i_reserved_data_blocks exception. + */ + path = ext4_find_extent(inode, ee_block, ppath, + flags | EXT4_EX_NOFAIL); + if (IS_ERR(path)) { + EXT4_ERROR_INODE(inode, "Failed split extent on %u, err %ld", + split, PTR_ERR(path)); + return PTR_ERR(path); + } + depth = ext_depth(inode); + ex = path[depth].p_ext; + *ppath = path; + if (EXT4_EXT_MAY_ZEROOUT & split_flag) { if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) { if (split_flag & EXT4_EXT_DATA_VALID1) { @@ -3342,7 +3361,7 @@ static int ext4_split_extent_at(handle_t *handle, ext4_ext_dirty(handle, inode, path + path->p_depth); return err; out: - ext4_ext_show_leaf(inode, path); + ext4_ext_show_leaf(inode, *ppath); return err; } -- 2.43.0