From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792863573; b=QZMIOFjgeo/7vqEMpyd7micZij+u839ag1sA0CetAwt1oBUrJ8TMAAmprk3vIGpHi+ff wPvNkGW1grhF+dQZjpZZf9XPUA2O9pDpGn8pyEWExEYsTHttl6ONt1YFNwbzGiB3bMQuB bEeVGcucRso3Uqa3bQ1XaG2QTMZANB4pCfOArF83LCXxRL56Er3wGZqJuAqtmoTllqqtq vGx/ns6XigmnV3+wN3+c68x2mnTK9eWsCsdHXcTpO7Zz9mrPRTZOuwwmOB+u+SpZi0wwe hC9VUH6Pd7GLePOVvzmzh/m5ehU5PsFALWTPH7yeaev1yj3RRa3hLOxfmSjdCyI1+Iw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792863573; h=Received:DKIM-Signature:Date:To:From:Subject:Message-Id; bh=ltZxm43WLsltiKzcI4YwjrkjSh75kf1koSoq85AHEn4=; b=kpg8StySXrM5mYr2h9ovBnzxeXDBJNUJiA0j0mkiHgADIck4LmqkgZTLzSk5eScr4DIV 2MkuGrK1wM077t1Op6i/e1Fb6Eo41GBSM97+8MKIP657ZCjDlUlqcxYat7hbs+aRCRrTV SlwXFckjO//UVY8yoXnQtEjLojfkUmtz0J3K6oB7owvA2nv2YjYzG0z2B8TRNpHNUPATz Pq8+zAayWCJdEbp0SQjMsvVCjZDOfzE9nx+IhmlOK043dwUvym3/aKecDyKdgnSmtasWr JwxOUwmbPZrs3fGYdwnoKCJd03EM104ZjqkKzsoewyapc6icrwLeLr2g8ZQ2xrTjchw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=hiAXQTiZ; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4A65D606A321; Sat, 24 Oct 2026 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=hiAXQTiZ Received: by smtp.kernel.org (Postfix) with ESMTPSA id C32B31F01825; Sat, 24 Oct 2026 17:39:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1792863572; bh=ltZxm43WLsltiKzcI4YwjrkjSh75kf1koSoq85AHEn4=; h=Date:To:From:Subject; b=hiAXQTiZDrjIK0bw7cqxMFkCumoV0BX1vaIE7djCN5o0Uo0kX08wD3SysiygvEzF/ ICqsQ4qArHQGn48x1J/sZQ3ZkZnKeuTQfBLy7G0HVnI6GXNWyOW5wZRXzu/hQL58B8 tkNy36Mh1AH++Jnb/kmJf0/KyZKxrrpkyDsC9FE4= Date: Sat, 24 Oct 2026 10:39:32 -0700 To: mm-commits@vger.kernel.org,stable@vger.kernel.org,mark@fasheh.com, jlbec@evilplan.org,heming.zhao@suse.com,joseph.qi@linux.alibaba.com, akpm@linux-foundation.org From: Andrew Morton Subject: + ocfs2-do-not-index-before-the-entry-array-when-dividing-an-empty-bucket.patch added to mm-nonmm-unstable branch Message-Id: <20261024173932.C32B31F01825@smtp.kernel.org> X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list The patch titled Subject: ocfs2: do not index before the entry array when dividing an empty bucket has been added to the -mm mm-nonmm-unstable branch. Its filename is ocfs2-do-not-index-before-the-entry-array-when-dividing-an-empty-bucket.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ocfs2-do-not-index-before-the-entry-array-when-dividing-an-empty-bucket.patch This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Joseph Qi Subject: ocfs2: do not index before the entry array when dividing an empty bucket Date: Sat, 24 Oct 2026 23:10:11 +0800 ocfs2_divide_xattr_bucket() appends an empty bucket carrying a sentinel hash when the source bucket has no divide position, taking that hash from xh_entries[start - 1]. ocfs2_xattr_find_divide_pos() returns count when every entry shares one hash, and its loop does not run at all for count < 2, so an empty bucket comes back with start == count == 0 and the read is xh_entries[-1]. That is outside the __counted_by_le(xh_count) bounds of xh_entries[] and lands on the header, so the value picked up is xh_count | xh_free_start << 16. One above it is written into the new bucket's xh_entries[0] and committed, which leaves a bucket whose first hash does not follow the bucket before it. ocfs2_xattr_bucket_find() binary searches on xh_entries[0], so the broken key hides the range the sentinel was meant to cover: getxattr() answers -ENODATA for an attribute that is stored, and an insert can go to the wrong bucket and leave two copies of a name. The cross cluster divide hands the same value back as a tree record's e_cpos, which then claims a hash range it does not cover. Read xh_entries[0] instead. The branch is only reached when every entry shares one hash, so for a non-empty bucket it holds the same value, and for an empty one it is the slot that carries the bucket key. An empty bucket reaches the divide from ocfs2_check_xattr_bucket_collision(), which reports no collision for one, through ocfs2_add_new_xattr_bucket() and ocfs2_extend_xattr_bucket(). It does not take a failed set to get there: a divide that finds no position is itself what leaves an empty sentinel bucket behind, and a later extend can pick it as the target. Link: https://lore.kernel.org/20261024151012.1059683-6-joseph.qi@linux.alibaba.com Fixes: 80bcaf3469b8 ("ocfs2/xattr: Proper hash collision handle in bucket division") Signed-off-by: Joseph Qi Signed-off-by: Andrew Morton Cc: Heming Zhao Cc: Mark Fasheh Cc: Joel Becker Cc: --- fs/ocfs2/xattr.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) --- a/fs/ocfs2/xattr.c~ocfs2-do-not-index-before-the-entry-array-when-dividing-an-empty-bucket +++ a/fs/ocfs2/xattr.c @@ -5228,7 +5228,15 @@ static int ocfs2_divide_xattr_bucket(str start = ocfs2_xattr_find_divide_pos(xh); if (start == count) { - xe = &xh->xh_entries[start-1]; + /* + * start == count means every entry shares one hash, so the + * first of them carries it too. An empty bucket has no + * entries[start - 1], but its entries[0] still carries the + * bucket key: either the hash ocfs2_xa_remove_entry() + * deliberately leaves behind, or the sentinel a previous + * divide wrote. + */ + xe = &xh->xh_entries[0]; /* * initialized a new empty bucket here. _ Patches currently in -mm which might be from joseph.qi@linux.alibaba.com are ocfs2-read-the-xattr-entry-hash-before-defragmenting-the-bucket.patch ocfs2-find-the-xattr-entry-again-after-defragmenting-a-bucket.patch ocfs2-find-the-xattr-entry-again-after-converting-a-block-to-a-bucket.patch ocfs2-do-not-read-the-entry-array-of-an-empty-xattr-bucket.patch ocfs2-do-not-index-before-the-entry-array-when-dividing-an-empty-bucket.patch ocfs2-do-not-read-the-entry-array-of-an-empty-xattr-block.patch