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=1794638838; b=piPiuuHaWotj4yO9cH4Xndr2j0jJ9BqNN9LjCvhfUKVJQNR/kNMPkQl1HJNq1hYyEOgB UcvGUYF8yblWRSguJQDyGYnxHFA0JgJOH2OnnN9qM8LCQaWtU36uhyB07th1IZaR7PU4H G1YF47y2lRbgFts/AnC51Oc1YFEOlYh/yMTt0poQetw/xP5idT/8Zi4NA+DlIjc/NZoH6 7G4fRYBAahVneS4VlqZwnZAf0uoqwQEpuRJHASHjXWA9BEnu1Bl4nOKashJXvXuU55SZE amNlxcXa8m0puiQy16yAzxBhLcX/RnjLHWlKoQR67oI39qdjmT1TA7LZk325+IjjsxA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794638838; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=KU2DGHJTqeFJpefLhYFgosKs8k0dlsxDE/9ISFruxTI=; b=LiAtdRrabPCBB18fp8R2ORYah+Ceh6L4xGzoB4Xb5PrtbXsiYHUopmMQm3Yhork/BVfv Lg5cgsMZNbfbOsMabZtV9X9vBgHc2foeoSS5HU9i/IDxPPz8lyGNe/JUNpfF9DdWITkIF VMOfHmz5IDekqZRWF5cjVqrv+InWoDKoebZEC1HNThjBT19cKb7HL6KT1a6V/p4PSvt6W 1qbjJXXMaCH3uOPxOCpTL8X8rV/4f3khIzmiDplJiSkqiUVnRzKhQcdlaJY0et5teNd0I 6SepBPa7SJIAXJN1Ny/ND76HMrMtfswWXiTKK+oPTUFM0mN3ITatOOjhlBAQg7y4lxg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=nrM8OWYP; 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 51010606A330 for ; Sat, 14 Nov 2026 06:47:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=nrM8OWYP Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6885F1F000C6; Sat, 14 Nov 2026 06:47:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794638838; bh=KU2DGHJTqeFJpefLhYFgosKs8k0dlsxDE/9ISFruxTI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nrM8OWYPlz0LjXHwRLcn1V/kaMWtGWORVW4N8ayn/GpgyB1IBs3tTBsKH85qe2ZS1 GPLD0ywPr05uokvos223Uogmza3BcU8cZ+lLuAhRHfFhemMfVlDVvOaB7VqDVmzAvg 1twmgmyvDcew2W/kG+cc9GCC5CLpmnOj57smokVWKLaEO0XnOnBH9luIL/h+R/w5Ff hIptbLoAt5Fr/0ZOvq4n24VEBkjApSujllVKXhvLXnzycWrlYkBiHuV+e2P1TD6hva Zuo1IjwS6g5kPyN5W0oi04Y3MFkiADpo+d2Iiz+EEu9o/5sHnBdirp2i56WUN+OhM5 /RQv6fVjZ9Nig== From: Sasha Levin To: stable@vger.kernel.org Cc: Joseph Qi , Andrew Morton , Heming Zhao , Mark Fasheh , Joel Becker , Sasha Levin Subject: [PATCH 6.1.y 2/2] ocfs2: do not read the entry array of an empty xattr bucket Date: Sat, 14 Nov 2026 01:47:15 -0500 Message-ID: <20261114064224.3223276-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261114064224.3223276-1-sashal@kernel.org> References: <20261109201729-failed-6.1-e8de099f2958@kernel.org> <20261114064224.3223276-1-sashal@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Joseph Qi [ Upstream commit e8de099f2958c84aa23186c5481e69f7ffd39355 ] ocfs2_check_xattr_bucket_collision() decides whether splitting a bucket can make room by comparing the hash being inserted against the first and the last entry. xh_count comes off disk and is never checked, and a bucket is allowed to hold no entries: ocfs2_xa_remove_entry() keeps the last slot when it removes the only one, so that an empty bucket still carries the hash it is keyed by. xh_count then reads back as 0 while xh_entries[0] is still meaningful, and the second comparison indexes xh_entries[-1]. That is outside the __counted_by_le(xh_count) bounds of xh_entries[] and lands on the header. An entry is 16 bytes and xe_name_hash is its first field, so the value read is xh_count | xh_free_start << 16. It stays inside the block, but the answer is arbitrary, and for an empty bucket it says there is no collision, so a new bucket gets added on the strength of it. An empty bucket holds no entries to collide with. Return before reading the array. One way to reach the test with an empty bucket is a set that removes the bucket's only entry during cleanup and then fails for space again, since it is that second -ENOSPC which calls this. Growing a value past OCFS2_XATTR_INLINE_SIZE is the easy route: the cluster allocation fails, the "!orig_clusters" arm of ocfs2_xa_cleanup_value_truncate() removes the entry, and although the "growing" caller does set ctxt->set_abort, only ocfs2_xattr_block_set() and __ocfs2_xattr_set_handle() look at it, so ocfs2_xattr_set_entry_index_block() goes straight on to the collision check. This sits on commit a9ea8b397864 ("ocfs2: use the stored hash when checking xattr bucket collision"), which gave the collision check its two argument form and is marked for 6.2 and later. The read fixed here is present in the three argument version too, but a tree without that commit needs the hunk adapted by hand. Link: https://lore.kernel.org/20261024151012.1059683-5-joseph.qi@linux.alibaba.com Fixes: 012255961c9e ("ocfs2: Enable xattr set in index btree") Signed-off-by: Joseph Qi Signed-off-by: Andrew Morton Cc: Heming Zhao Cc: Mark Fasheh Cc: Joel Becker Cc: Signed-off-by: Sasha Levin --- fs/ocfs2/xattr.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c index fca9ed94ca17a..49b1b4e072ce3 100644 --- a/fs/ocfs2/xattr.c +++ b/fs/ocfs2/xattr.c @@ -5609,11 +5609,20 @@ static int ocfs2_check_xattr_bucket_collision(struct ocfs2_xattr_bucket *bucket, u32 name_hash) { struct ocfs2_xattr_header *xh = bucket_xh(bucket); + u16 count = le16_to_cpu(xh->xh_count); + + /* + * An empty bucket keeps the hash of the entry that was removed in + * xh_entries[0] so that it can still be found, but it holds no + * entries to collide with. + */ + if (!count) + return 0; if (name_hash != le32_to_cpu(xh->xh_entries[0].xe_name_hash)) return 0; - if (xh->xh_entries[le16_to_cpu(xh->xh_count) - 1].xe_name_hash == + if (xh->xh_entries[count - 1].xe_name_hash == xh->xh_entries[0].xe_name_hash) { mlog(ML_ERROR, "Too much hash collision in xattr bucket %llu, " "hash = %u\n", -- 2.53.0