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=1793663128; b=ddju3V41aKf8hnUjSsyg17wnMagi7Sc22Itl+1PrQoeePcKJpNYatpw3C4U2kgGych4l agqYwjM8cmREwT34Fsw0LBXeJWPctZG6Yin2EFQEhvizfw1q/B0YvMFENqpj2LaV5sbW5 YwWMiL5GanaD5c/NSvB0XmCpLy9WSticB7DAIvksHdUE+20Rh2PlHdm/Iq2p0qTJkQ9fr xC2ZpoId4A+JA3UwBbjK2xgCWEuLYCOApUZfzjckxoY08c7EkHplzFhFSSXZ7bjeXPvbB O4tMOElPz4YCJAbzFlzkdT0J8M3h+nx6YO1lmtWGg4oVTKN2KmMJN9phJXXgwXgcdmA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793663128; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=EHiF5cSD0SeACs8er5oOSSGUf9vIit/oZi2eyqsY6Jc=; b=pztLdC2dGrVtqsPdZQRrBKW99xtcFKkimd0IZ7u38oiPTe9wu19DrGFtMsUlVrVh3pz/ 7700EkbamGCLXaQswoPUXVhmhxEp7Up5uldp/9JOfq6mQCa5FM1ZCi/UG1EW4fQHwgNlb LTf2Vsh4NOCUYDZq5ln/FgevY8fsV72+LWDx6s4SZmC9fuYBB1gauwqUVKh/m9k9UyzQN cmrnIkzRY6V1JrrpF9RSJ2IXhybfEa3WgxjMpvahw58Pvr0cTstzTbTtW0qQIxVGtcPu1 Jn6VZtSShfeGVs5LxDOD6EpDstnAH+duemgt8ptmTBak+Hp3QYlh7XGk4Ucgo0Kd5tQ== 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=e54nDZFH; 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 5838E606A327 for ; Mon, 2 Nov 2026 23:45:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=e54nDZFH Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69C551F00A16; Mon, 2 Nov 2026 23:45:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793663127; bh=EHiF5cSD0SeACs8er5oOSSGUf9vIit/oZi2eyqsY6Jc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=e54nDZFHRONsgtSF8+CU4hLcvSNcqbPASGyp2cjerWqY1ES42aHzyIcA4OFRcV+SC wnytRZPFpmbYCJ8n73yvfjtPHRT+QwSGtxfWZdL+lEZcVvFvd1JokN0oJGJubpy7bl O2G3ri9A+olk5gpNmtZVOpG++/Y6QdPp1lRhpLTzYH+pl5atOS8V+DqBXFyG8BZ80w S33Owoy+0wLu5/3O7XegMVnkzYX4HOHRDHC/3JtLjnu/zjBqAVqU/ii+Z0LOKqnex0 kwsock+wp9rBsBvTsxmFRxdL65xBxx60LNKqLQoQARdNNFIiIpgk4Lf83p88MH4QGj T1E/7Gz+7B55w== From: Sasha Levin To: stable@vger.kernel.org Cc: Yongjun Gwon , Namjae Jeon , Sasha Levin Subject: [PATCH 6.1.y] ksmbd: serialize directory emptiness checks with readdir Date: Mon, 2 Nov 2026 18:45:26 -0500 Message-ID: <20261102234410.2575558-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110243-apostle-blitz-3a1e@gregkh> References: <2026110243-apostle-blitz-3a1e@gregkh> 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: Yongjun Gwon [ Upstream commit 7220980b2423d06a0604516129bfa4cec8a697ae ] SMB2 QUERY_DIRECTORY holds fp->readdir_lock while it calls iterate_dir() on fp->filp. An SMB2 SET_INFO request with FILE_DISPOSITION_INFORMATION can resolve the same FileId and call ksmbd_vfs_empty_dir() on the same filp without that lock. iterate_dir()'s inode read lock permits concurrent readers and does not serialize per-file iterator state. ext4 stores its dx readdir cursor and fname RB tree in file->private_data. Concurrent reset or refill can therefore free a fname node while the other worker still traverses it or retains its RB-tree link, resulting in use-after-free accesses. An authenticated SMB client with list and delete rights on a directory in a writable KSMBD share backed by ext4 can trigger this when the directory takes the dx readdir path. The client overlaps an SMB2 QUERY_DIRECTORY request with an SMB2 SET_INFO request carrying FILE_DISPOSITION_INFORMATION on one live FileId. In one x86_64 SMP KASAN multi-shot guest using ksmbd-for-next at 171df27077fb, the unmodified kernel reported a cross-worker use-after-free before a panic. The first report's access and free stacks show the two request paths directly (trimmed): BUG: KASAN: slab-use-after-free in ext4_htree_store_dirent+0x488/0x550 Read of size 8 by task kworker/2:0/29 Workqueue: ksmbd-io handle_ksmbd_work Call Trace: ext4_htree_store_dirent+0x488/0x550 htree_dirblock_to_tree+0x535/0x990 ext4_htree_fill_tree+0x319/0xba0 ext4_readdir+0x175a/0x2f40 iterate_dir+0x1b6/0x630 smb2_query_dir+0x1003/0x1cc0 Freed by task 279: free_rb_tree_fname+0x67/0xc0 ext4_readdir+0x13a9/0x2f40 iterate_dir+0x1b6/0x630 ksmbd_vfs_empty_dir+0xa2/0x100 smb2_set_info+0x2ffa/0x45d0 Take fp->readdir_lock across the entire emptiness check. This places both iterators over that handle's filp in the same lock domain while preserving the disposition status handling. The exact code change completed a warning-free x86_64 KASAN bzImage build. Tracing three request pairs showed that the two iterate_dir() calls no longer overlapped and the expected statuses were preserved. A further 1,600 reproducer iterations completed with expected statuses and no KASAN report, Oops, or panic. The reproducer and complete guest configuration are available privately to maintainers on request. Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Yongjun Gwon Signed-off-by: Namjae Jeon [ sashal: omitted the ksmbd_stream_fd() exclusion from the directory condition ] Signed-off-by: Sasha Levin --- fs/smb/server/smb2pdu.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index 1c13f359ac0cf..895c5dcfad617 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -6089,6 +6089,7 @@ static int set_file_disposition_info(struct ksmbd_work *work, struct smb2_file_disposition_info *file_info) { struct inode *inode; + int err; if (!(fp->daccess & FILE_DELETE_LE)) { pr_err("no right to delete : 0x%x\n", fp->daccess); @@ -6097,9 +6098,13 @@ static int set_file_disposition_info(struct ksmbd_work *work, inode = file_inode(fp->filp); if (file_info->DeletePending) { - if (S_ISDIR(inode->i_mode) && - ksmbd_vfs_empty_dir(fp) == -ENOTEMPTY) - return -EBUSY; + if (S_ISDIR(inode->i_mode)) { + mutex_lock(&fp->readdir_lock); + err = ksmbd_vfs_empty_dir(fp); + mutex_unlock(&fp->readdir_lock); + if (err == -ENOTEMPTY) + return -EBUSY; + } smb_break_all_levII_oplock(work, fp, 0); ksmbd_set_inode_pending_delete(fp); } else { -- 2.53.0