From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 8FCCE356A0D; Sat, 12 Sep 2026 10:14:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789208073; cv=none; b=c3Nf5gsNbpwmOul3Sp9Bswej4ihd+Xo1k41Y3YOGUNHeibqyx3jISJAVCG2GWnPdN1FkfRgUhwhEx0FhhOFl5nTVR0B99EFk3DNKJlhkzTZjRMrpOWIMYYHOCkj7m8VjBmIqALx8j6RF39B+9jH3xpC9FD0ZG4EWWoyanc5YOHA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789208073; c=relaxed/simple; bh=h2A76TrmocHsR8Q2dJWtB5stGNe85vE2NAs1aIbZnKQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OAMflRmmwKEvA7SIFEejn2Lv4DdjEcH2tmgCOBFcGZsZffYFOIlC2i6CwPUBeaYDVpJ+fdoWbn0xS3dnaDoKV05011LQXjs0DkAXT+FxFr+2lTVj2VlmsZ+kGP1pF5AQDaH1T3YFcLBB+GfO9N4H6Bu9Cj33/fYUtadrRHTJQxw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BaPw6Kdl; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="BaPw6Kdl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9472E1F000FF; Sat, 12 Sep 2026 10:14:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789208072; bh=A4pO0HF8xT/+BPXyyyexlZWUVLxqIGsANbQLsjdMPyw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=BaPw6KdlS16bm8XX1ur1ozNVb9Jud1qznJS8ONVZ479RUB0sjZCm8OeoScp+VM3Gc hpQEQg1cCB0DZNYd0RL9NMGC1bjanq53zeHmIZRWMX76fN61qRkxggmuBTyNv5ZBZz Of749EZMprp3j7Mo5lWPXOYv8wOLSdFDYB0EnLBE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Weiming Shi , Xiang Mei , Andreas Dilger , Jan Kara , Theodore Tso , Sasha Levin Subject: [PATCH 6.18 0542/1518] ext4: check dir entry fits before reading the hash trailer in ext4_search_dir() Date: Sat, 12 Sep 2026 08:45:11 +0200 Message-ID: <20260912065635.704188458@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065623.398859879@linuxfoundation.org> References: <20260912065623.398859879@linuxfoundation.org> User-Agent: quilt/0.69 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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Xiang Mei [ Upstream commit c7e6b863d298f56522d0d08554bbea7f142e6588 ] For casefolded encrypted directories ext4 stores an 8-byte hash trailer after the name (EXT4_DIRENT_HASHES()), at an offset derived from de->name_len. On the sb_no_casefold_compat_fallback() path ext4_match() reads that trailer, but ext4_search_dir()'s by-hand pre-check only tests de->name + de->name_len <= dlimit, which proves the name fits, not the rounded trailer. A crafted entry whose name ends at the block boundary passes the check while EXT4_DIRENT_HASHES(de) lands past the block end, so ext4_match() reads out of bounds on an ordinary lookup. KASAN reports it as a use-after-free when the page after the directory block holds a freed object: BUG: KASAN: use-after-free in ext4_match (fs/ext4/namei.c:1435) Read of size 4 at addr ffff888010458000 by task exploit Call Trace: ext4_match (fs/ext4/namei.c:1435) ext4_search_dir (fs/ext4/namei.c:1470) __ext4_find_entry (fs/ext4/namei.c:1268 fs/ext4/namei.c:1632) ext4_lookup (fs/ext4/namei.c:1703 fs/ext4/namei.c:1769) ... filename_lookup (fs/namei.c:2842) vfs_statx (fs/stat.c:353) __do_sys_newfstatat (fs/stat.c:538) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Require, for hash-in-dirent directories, that the whole entry including the rounded trailer fits before calling ext4_match(). This is the same bound ext4_check_dir_entry() already enforces via ext4_dir_rec_len(), so no well-formed entry is rejected. The other caller, ext4_find_dest_de(), runs ext4_check_dir_entry() first and is unaffected. Fixes: 471fbbea7ff7 ("ext4: handle casefolding with encryption") Reported-by: Weiming Shi Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Xiang Mei Reviewed-by: Andreas Dilger Reviewed-by: Jan Kara Link: https://patch.msgid.link/20260709184101.441348-1-xmei5@asu.edu Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- fs/ext4/namei.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 2e35453a56f28..2c661155158f8 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -1467,6 +1467,8 @@ int ext4_search_dir(struct buffer_head *bh, char *search_buf, int buf_size, /* this code is executed quadratically often */ /* do minimal checking `by hand' */ if (de->name + de->name_len <= dlimit && + (!ext4_hash_in_dirent(dir) || + (char *)de + ext4_dir_rec_len(de->name_len, dir) <= dlimit) && ext4_match(dir, fname, de)) { /* found a match - just to be sure, do * a full check */ -- 2.53.0