From nobody Fri Dec 19 22:01:37 2025 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 17325269CF0; Tue, 8 Apr 2025 11:04:03 +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=1744110244; cv=none; b=LQSURtsHjlpzQv/yaHMqH+ksXxNb2/6bGajNz0zIitHZUG7FwgooYWiLH3n/TI5GFaRYyRQpSoLtRePXUmEnhfkgEVDPBpsmzQzYeY5PwbdBPl3iAZeVqVckX5ibifSuM4pAdiJ0E1/JAfz3MAPOKs2ntMTQA7eiVEUrjEe/4F0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744110244; c=relaxed/simple; bh=eF8ykuB3zv9H36H3ho5AqA1fkqlQywk4736N5EJ2uVM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kc7p19yv2Xyqna2zbYqfUxhn+WiDjk/XGN+0iMjFUss3qcdOdOTlazjgPstfwkch+v8jRRQz4+gqHGxZfROMFM1zYbjbhNrpxW2+I6acF07lHVtK1YEA7FLRPivx21vOELov2Me1g6KjNGRiFdEsoD8c1iUNyZuskO/JmavgrZU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=h6B0Jzrj; 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="h6B0Jzrj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 35C8CC4CEE5; Tue, 8 Apr 2025 11:04:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744110243; bh=eF8ykuB3zv9H36H3ho5AqA1fkqlQywk4736N5EJ2uVM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=h6B0JzrjLdW1aaQX/sBoTjFHeefoXkJPG4hutp3k721udh3TBJhqYBFzc875BzTWA P7sGWFJwVqY2W4jJtK9tkh+0FAJxl6i2pTo/4d7M1NdMyYuhCbCMKy0fg3T5b826jd f63A1xgZ6P1gNJIJ8vEQx/lydT29LEUpNQ4C1Ox4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jakub Acs , Theodore Tso , Andreas Dilger , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, Mahmoud Adam , security@kernel.org Subject: [PATCH 5.10 221/227] ext4: fix OOB read when checking dotdot dir Date: Tue, 8 Apr 2025 12:49:59 +0200 Message-ID: <20250408104826.925865160@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250408104820.353768086@linuxfoundation.org> References: <20250408104820.353768086@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Acs, Jakub commit d5e206778e96e8667d3bde695ad372c296dc9353 upstream. Mounting a corrupted filesystem with directory which contains '.' dir entry with rec_len =3D=3D block size results in out-of-bounds read (later on, when the corrupted directory is removed). ext4_empty_dir() assumes every ext4 directory contains at least '.' and '..' as directory entries in the first data block. It first loads the '.' dir entry, performs sanity checks by calling ext4_check_dir_entry() and then uses its rec_len member to compute the location of '..' dir entry (in ext4_next_entry). It assumes the '..' dir entry fits into the same data block. If the rec_len of '.' is precisely one block (4KB), it slips through the sanity checks (it is considered the last directory entry in the data block) and leaves "struct ext4_dir_entry_2 *de" point exactly past the memory slot allocated to the data block. The following call to ext4_check_dir_entry() on new value of de then dereferences this pointer which results in out-of-bounds mem access. Fix this by extending __ext4_check_dir_entry() to check for '.' dir entries that reach the end of data block. Make sure to ignore the phony dir entries for checksum (by checking name_len for non-zero). Note: This is reported by KASAN as use-after-free in case another structure was recently freed from the slot past the bound, but it is really an OOB read. This issue was found by syzkaller tool. Call Trace: [ 38.594108] BUG: KASAN: slab-use-after-free in __ext4_check_dir_entry+0x= 67e/0x710 [ 38.594649] Read of size 2 at addr ffff88802b41a004 by task syz-executor= /5375 [ 38.595158] [ 38.595288] CPU: 0 UID: 0 PID: 5375 Comm: syz-executor Not tainted 6.14.= 0-rc7 #1 [ 38.595298] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS = rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 38.595304] Call Trace: [ 38.595308] [ 38.595311] dump_stack_lvl+0xa7/0xd0 [ 38.595325] print_address_description.constprop.0+0x2c/0x3f0 [ 38.595339] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595349] print_report+0xaa/0x250 [ 38.595359] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595368] ? kasan_addr_to_slab+0x9/0x90 [ 38.595378] kasan_report+0xab/0xe0 [ 38.595389] ? __ext4_check_dir_entry+0x67e/0x710 [ 38.595400] __ext4_check_dir_entry+0x67e/0x710 [ 38.595410] ext4_empty_dir+0x465/0x990 [ 38.595421] ? __pfx_ext4_empty_dir+0x10/0x10 [ 38.595432] ext4_rmdir.part.0+0x29a/0xd10 [ 38.595441] ? __dquot_initialize+0x2a7/0xbf0 [ 38.595455] ? __pfx_ext4_rmdir.part.0+0x10/0x10 [ 38.595464] ? __pfx___dquot_initialize+0x10/0x10 [ 38.595478] ? down_write+0xdb/0x140 [ 38.595487] ? __pfx_down_write+0x10/0x10 [ 38.595497] ext4_rmdir+0xee/0x140 [ 38.595506] vfs_rmdir+0x209/0x670 [ 38.595517] ? lookup_one_qstr_excl+0x3b/0x190 [ 38.595529] do_rmdir+0x363/0x3c0 [ 38.595537] ? __pfx_do_rmdir+0x10/0x10 [ 38.595544] ? strncpy_from_user+0x1ff/0x2e0 [ 38.595561] __x64_sys_unlinkat+0xf0/0x130 [ 38.595570] do_syscall_64+0x5b/0x180 [ 38.595583] entry_SYSCALL_64_after_hwframe+0x76/0x7e Fixes: ac27a0ec112a0 ("[PATCH] ext4: initial copy of files from ext3") Signed-off-by: Jakub Acs Cc: Theodore Ts'o Cc: Andreas Dilger Cc: linux-ext4@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: Mahmoud Adam Cc: stable@vger.kernel.org Cc: security@kernel.org Link: https://patch.msgid.link/b3ae36a6794c4a01944c7d70b403db5b@amazon.de Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/ext4/dir.c | 3 +++ 1 file changed, 3 insertions(+) --- a/fs/ext4/dir.c +++ b/fs/ext4/dir.c @@ -88,6 +88,9 @@ int __ext4_check_dir_entry(const char *f else if (unlikely(le32_to_cpu(de->inode) > le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count))) error_msg =3D "inode out of bounds"; + else if (unlikely(next_offset =3D=3D size && de->name_len =3D=3D 1 && + de->name[0] =3D=3D '.')) + error_msg =3D "'.' directory cannot be the last in data block"; else return 0;