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=1793633264; b=Zp5/fqjGDjOyXddAeZ5BaHLoKRzzHTju4KwPddkSg+1ypYULI4Wy7ZAXPmCF89GzH4zq /X3ZfJPJgti73ceq71gW6Ej2nP9tQbpjcBCyoo4cbhqwRYOubiM8Jw0mzPWCXg/ZDuC/K H/r4ouhrvDsQCG4qe24IiDpCoMNZdjc2AYNuK1S8329mW8GaNCyC5BDTuCkTyxo9N1KlX mzRVmI0EGMdBeJy+7o+pSAE3HoU8+N8TLP4fll8popnMoXWLzgpCCRqYVNjtAofz3Voyk qmcPY7pJaC1ntjhBfa1jbwtpeOUO7P1w/fYv6gLl61LxGwQS9T8qOX3DgmvDM0i9Nvg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793633264; h=Received:DKIM-Signature:Subject:To:Cc:From:Date:Message-ID: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=RCLREU3ug6s0nq3vvgZoAVXVzQ57l3I6oW/fEoaBMow=; b=3SEDMVve+xOzzw+n9V85yX67os1YM5kWNbZ4oBPM7MM0nO+DpvbQoSNrj0Dzx7bw37BV /RoXADu1Ux2pVgzLaNAAXx+bzR2U5UUDwQuAzTkZAEphFd8D93l38ZJClqBUSB7isWBKE iWHts5qxV1JdyQqoL0pxvPIEgTGGc1sJw9ZL2DyCcK3NvjAaoZRbc5o2WKTvWV6gzLYMU SQPiKduifKaddh33wGX4aXjBmTKBDnfJrsNRq0Bc2YrtRnPf4UEHyJ58i9TWT7Hy0iE3K 7eK9wOXMefyfkmKp55WRAUaeR6GQ5bHkjqQqOn4vsg4NUrLR6MAUHP5davsc4o2WHJg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=kUhxPalx; 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 6BBE4609C7E5 for ; Mon, 2 Nov 2026 15:27:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=kUhxPalx Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93A701F00A1B; Mon, 2 Nov 2026 15:27:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793633263; bh=RCLREU3ug6s0nq3vvgZoAVXVzQ57l3I6oW/fEoaBMow=; h=Subject:To:Cc:From:Date; b=kUhxPalxzD/hHe08wSGoYf0/1h1WOwNlor/jB+juATdY+FZG8Ky4xfY8FPK6+p4EO lz7yZPangqneNzfz99gigX0tduPcnW02g3Iop575bLEijk/mqBvJcOEp/dLL1Igu3P z0PhUJOgtqgO4ssVUeV+W6YINL513lvnOpgx0j8E= Subject: FAILED: patch "[PATCH] ksmbd: serialize directory emptiness checks with readdir" failed to apply to 6.12-stable tree To: d3bugee@gmail.com,linkinjeon@kernel.org Cc: From: Date: Mon, 02 Nov 2026 16:27:41 +0100 Message-ID: <2026110241-arrest-granny-ae4b@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-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 7220980b2423d06a0604516129bfa4cec8a697ae # git commit -s git send-email --to '' --in-reply-to '2026110241-arrest-granny-ae4b@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 7220980b2423d06a0604516129bfa4cec8a697ae Mon Sep 17 00:00:00 2001 From: Yongjun Gwon Date: Fri, 23 Oct 2026 02:38:32 +0900 Subject: [PATCH] ksmbd: serialize directory emptiness checks with readdir 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 diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index da82d80c222a..f5fe3cf8ba32 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -8918,6 +8918,7 @@ 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); @@ -8932,9 +8933,13 @@ static int set_file_disposition_info(struct ksmbd_work *work, if (ksmbd_has_stream_without_delete_share(fp)) return -ESHARE; - if (S_ISDIR(inode->i_mode) && !ksmbd_stream_fd(fp) && - ksmbd_vfs_empty_dir(fp) == -ENOTEMPTY) - return -EBUSY; + if (S_ISDIR(inode->i_mode) && !ksmbd_stream_fd(fp)) { + 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_for_delete(work, fp); ksmbd_fd_set_delete_pending(fp); } else {