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 4B3D83F9F25 for ; Wed, 16 Sep 2026 08:48:49 +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=1789548531; cv=none; b=W1AO12mIbR1jAEuneG1/4wvk8mGA8+Ei/adFqAmA/VYWJWrfQy7gOLGZV3J3SP9Q1n+iIBOCoBT+Ut84YO4DuQyvFFbrI8t9LUKrz+N8PJQRjvXGEYMcwbG+qB3Ysi2z6dGs48sIbheYXjEEPki+YeZhaR67ARam8eKXVQAHaU4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789548531; c=relaxed/simple; bh=ePJLJnuaGCJMjAOukfLg0pHbTp+xQ9SBsjzeJiNOMgE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=DS17iCEc5Ayp7gedKY60zwo6kV8qVLJbO9BVItyQZ6MKSG/NuhLsrNk156jm120D1QPqS0hypAwATHPy1QBabaim4iKRp0YROTSJ2FK8LOuGvuw6SC1svQwNEXaEyYOnf96OIr1JIiAoQEWtocarrmXcOFkJCwU99qWugvovXFM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=YuxHOpy0; 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="YuxHOpy0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1ED9C1F000FF; Wed, 16 Sep 2026 08:48:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789548529; bh=25aC+JMaB3EkmoE1De+tdy1dbmWzSy9TRb09uzNRTt0=; h=From:To:Cc:Subject:Date:Reply-To; b=YuxHOpy0uTCYKddO6wDLjI10xHu5+z79RZJzerjeg8AtQ3F2qvWEagR5+2YjWF7yz b3HbFblFiJOkfEi8uhACw056q5r4niqjUP+X1btTvmps1z65Xy7xXtGe0xUFlX6YJR yKOGBkfUHz8QwzUV2M++kxf88vRyLWIBSSyZbw0Q= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-89787: ext4: check dir entry fits before reading the hash trailer in ext4_search_dir() Date: Wed, 16 Sep 2026 09:46:51 +0100 Message-ID: <2026091641-CVE-2026-89787-56bb@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4527; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=5HqhCy068lTfAw4/Pb/NAdiwTRGhl5eVuSPuAWvwCVw=; b=owGbwMvMwCRo6H6F97bub03G02pJDFmrwotcZTZfaNU/w8eoq35GVoPTVXuv7cNzbc4MO2rsf c5e357cEcvCIMjEICumyPJlG8/R/RWHFL0MbU/DzGFlAhnCwMUpABNp62NYcD2/emeTxxOd6R6n H8Xt472jtTr2GsOCVbu9Mz/kvChaY50x+cl2ccNtezYsBgA= X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: ext4: check dir entry fits before reading the hash trailer in ext4_search_dir() 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. The Linux kernel CVE team has assigned CVE-2026-89787 to this issue. Affected and fixed versions =========================== Issue introduced in 5.13 with commit 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 and fixed in 5.15.221 with commit 4d20106c536b73c4a8a02652dc85e35898baebf7 Issue introduced in 5.13 with commit 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 and fixed in 6.1.188 with commit 61a395967de06edba58760e81907a272db749faa Issue introduced in 5.13 with commit 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 and fixed in 6.6.157 with commit e94676a08af6312aa72d8a981232b281f9bcfcf5 Issue introduced in 5.13 with commit 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 and fixed in 6.12.110 with commit d8c184bec24b5a00ae96d704856d935eaded1685 Issue introduced in 5.13 with commit 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 and fixed in 6.18.52 with commit 3933884bc3102898b458c53fbd1ac52eb9cdb8a4 Issue introduced in 5.13 with commit 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 and fixed in 7.2.6 with commit 83663c0b739480c00cfe785675db87520ec484ed Issue introduced in 5.13 with commit 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 and fixed in 7.3-rc1 with commit c7e6b863d298f56522d0d08554bbea7f142e6588 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-89787 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/ext4/namei.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/4d20106c536b73c4a8a02652dc85e35898baebf7 https://git.kernel.org/stable/c/61a395967de06edba58760e81907a272db749faa https://git.kernel.org/stable/c/e94676a08af6312aa72d8a981232b281f9bcfcf5 https://git.kernel.org/stable/c/d8c184bec24b5a00ae96d704856d935eaded1685 https://git.kernel.org/stable/c/3933884bc3102898b458c53fbd1ac52eb9cdb8a4 https://git.kernel.org/stable/c/83663c0b739480c00cfe785675db87520ec484ed https://git.kernel.org/stable/c/c7e6b863d298f56522d0d08554bbea7f142e6588