From mboxrd@z Thu Jan 1 00:00:00 1970 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 9B55F347C6; Mon, 29 Dec 2025 16:16:53 +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=1767025013; cv=none; b=DJeDCdivIbiGhZT4eNvFFgFB3XxB2sftO4myn41L/Hf1h/nPqsrbuucBUZbAYfmVcymnReRM303QuKzZz+XsjojJeg34ZZZwQVrfOmj146oRm2X5VLUP282bDeUWNGcDW0ijC4WcjRqAtCc/Jtvd3U7TB4gRONiqOcKX4Si8+pY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767025013; c=relaxed/simple; bh=tz6ymlzumdUMGJe/hYog/GOPj5snTItYjRz0DyLG3Vg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KMLomNkBteT6b3D4HcirXmfC02n9KJDCgohz6o2rFqXl2Bum+Sk8/J99BsL6zYXu/n5eulEID6d0X9rvddiA53Mu8y1REvNP1kCvxuA44AEj0cYYacpiCeq4AP5GlMRdGgWzIoqwCt2xRFtVyM5izPiW4tOeeDxn+nrApFaIXyU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=HxJ/axSn; 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="HxJ/axSn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1C42BC4CEF7; Mon, 29 Dec 2025 16:16:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767025013; bh=tz6ymlzumdUMGJe/hYog/GOPj5snTItYjRz0DyLG3Vg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HxJ/axSnUbMbKfRUvVZEBlz3+mfPg3UXvWDd2IXjwr5VK1jswQLQYNdbvWftgT1AE bZ6xm1GQgioSzg/zhhhpxLza3pvp4IM8clMfurpRYUnPhA2H2el9SlqmH4Gpt03Mng wkFBDRIvNh7G8/ohFvdk3AuD0B2SQDBf56pza5N8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+005d2a9ecd9fbf525f6a@syzkaller.appspotmail.com, Yang Chenzhi , Viacheslav Dubeyko , Sasha Levin Subject: [PATCH 6.18 030/430] hfsplus: fix missing hfs_bnode_get() in __hfs_bnode_create Date: Mon, 29 Dec 2025 17:07:12 +0100 Message-ID: <20251229160725.269200462@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251229160724.139406961@linuxfoundation.org> References: <20251229160724.139406961@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: Yang Chenzhi [ Upstream commit 152af114287851583cf7e0abc10129941f19466a ] When sync() and link() are called concurrently, both threads may enter hfs_bnode_find() without finding the node in the hash table and proceed to create it. Thread A: hfsplus_write_inode() -> hfsplus_write_system_inode() -> hfs_btree_write() -> hfs_bnode_find(tree, 0) -> __hfs_bnode_create(tree, 0) Thread B: hfsplus_create_cat() -> hfs_brec_insert() -> hfs_bnode_split() -> hfs_bmap_alloc() -> hfs_bnode_find(tree, 0) -> __hfs_bnode_create(tree, 0) In this case, thread A creates the bnode, sets refcnt=1, and hashes it. Thread B also tries to create the same bnode, notices it has already been inserted, drops its own instance, and uses the hashed one without getting the node. ``` node2 = hfs_bnode_findhash(tree, cnid); if (!node2) { <- Thread A hash = hfs_bnode_hash(cnid); node->next_hash = tree->node_hash[hash]; tree->node_hash[hash] = node; tree->node_hash_cnt++; } else { <- Thread B spin_unlock(&tree->hash_lock); kfree(node); wait_event(node2->lock_wq, !test_bit(HFS_BNODE_NEW, &node2->flags)); return node2; } ``` However, hfs_bnode_find() requires each call to take a reference. Here both threads end up setting refcnt=1. When they later put the node, this triggers: BUG_ON(!atomic_read(&node->refcnt)) In this scenario, Thread B in fact finds the node in the hash table rather than creating a new one, and thus must take a reference. Fix this by calling hfs_bnode_get() when reusing a bnode newly created by another thread to ensure the refcount is updated correctly. A similar bug was fixed in HFS long ago in commit a9dc087fd3c4 ("fix missing hfs_bnode_get() in __hfs_bnode_create") but the same issue remained in HFS+ until now. Reported-by: syzbot+005d2a9ecd9fbf525f6a@syzkaller.appspotmail.com Signed-off-by: Yang Chenzhi Signed-off-by: Viacheslav Dubeyko Link: https://lore.kernel.org/r/20250829093912.611853-1-yang.chenzhi@vivo.com Signed-off-by: Viacheslav Dubeyko Signed-off-by: Sasha Levin --- fs/hfsplus/bnode.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c index edf7e27e1e375..482a6c5faa197 100644 --- a/fs/hfsplus/bnode.c +++ b/fs/hfsplus/bnode.c @@ -481,6 +481,7 @@ static struct hfs_bnode *__hfs_bnode_create(struct hfs_btree *tree, u32 cnid) tree->node_hash[hash] = node; tree->node_hash_cnt++; } else { + hfs_bnode_get(node2); spin_unlock(&tree->hash_lock); kfree(node); wait_event(node2->lock_wq, -- 2.51.0