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 D9B5435B13C for ; Wed, 28 Jan 2026 14:34:25 +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=1769610865; cv=none; b=WA0ZtpS7uPZTsKKxGvYJ/0py7EJoz0CDCAkPYwtLfTAdvoy6lJ208aWnbPDD6N2sTD6CjLvkl4No6jdqMVN563Gw93+zq//0ix3QvVBNLfAqk7xRDoKXI6aoIIyti69T1sPW1xMYPCFzwRz5WbUD5VUioAhcc11BXhIrPcM4HoI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769610865; c=relaxed/simple; bh=bNAD/iosu7dkox4pFpyAGIeJs6s0a4t0hd5xz94V3Aw=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=GCJEPvpZmkSNmOJAAEhjRGEh+1vMpkiqBLhOxHI6lQ0KytBHNBaqodlLFCEebeYbffwI7ohA2q1/Qn/O3pJpiP8H4+Dv5nkliNyOwY/Yk7hzEmba9OOpDiAQjFMoy2GCkH66VsK6I05ycIaN1QmzeBWMuEzRpOcPq6Oy8CFpgiQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BEObbmdA; 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="BEObbmdA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2F5EDC4CEF1; Wed, 28 Jan 2026 14:34:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1769610865; bh=bNAD/iosu7dkox4pFpyAGIeJs6s0a4t0hd5xz94V3Aw=; h=Subject:To:Cc:From:Date:From; b=BEObbmdAvw0xIg0kLhcxNu5A9msI3GjFh3E3ISSbmaxNczLsLLdZFpv62kPEXSixy W3WSYLpXjt3J4KZeiVb2lvfs7gbdTaJyrfnQ6CBSHeeeSvbTdOTpJ8S/uYoRCY0wvQ H6s7WMAqJLubmEplbXFe5o+R9S1F2+pIuIJDUGp8= Subject: FAILED: patch "[PATCH] ksmbd: Fix race condition in RPC handle list access" failed to apply to 6.6-stable tree To: ysk@kzalloc.com,linkinjeon@kernel.org,stfrench@microsoft.com Cc: From: Date: Wed, 28 Jan 2026 15:34:22 +0100 Message-ID: <2026012822-pennant-explore-e187@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x 305853cce379407090a73b38c5de5ba748893aee # git commit -s git send-email --to '' --in-reply-to '2026012822-pennant-explore-e187@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 305853cce379407090a73b38c5de5ba748893aee Mon Sep 17 00:00:00 2001 From: Yunseong Kim Date: Mon, 15 Sep 2025 22:44:09 +0000 Subject: [PATCH] ksmbd: Fix race condition in RPC handle list access The 'sess->rpc_handle_list' XArray manages RPC handles within a ksmbd session. Access to this list is intended to be protected by 'sess->rpc_lock' (an rw_semaphore). However, the locking implementation was flawed, leading to potential race conditions. In ksmbd_session_rpc_open(), the code incorrectly acquired only a read lock before calling xa_store() and xa_erase(). Since these operations modify the XArray structure, a write lock is required to ensure exclusive access and prevent data corruption from concurrent modifications. Furthermore, ksmbd_session_rpc_method() accessed the list using xa_load() without holding any lock at all. This could lead to reading inconsistent data or a potential use-after-free if an entry is concurrently removed and the pointer is dereferenced. Fix these issues by: 1. Using down_write() and up_write() in ksmbd_session_rpc_open() to ensure exclusive access during XArray modification, and ensuring the lock is correctly released on error paths. 2. Adding down_read() and up_read() in ksmbd_session_rpc_method() to safely protect the lookup. Fixes: a1f46c99d9ea ("ksmbd: fix use-after-free in ksmbd_session_rpc_open") Fixes: b685757c7b08 ("ksmbd: Implements sess->rpc_handle_list as xarray") Cc: stable@vger.kernel.org Signed-off-by: Yunseong Kim Acked-by: Namjae Jeon Signed-off-by: Steve French diff --git a/fs/smb/server/mgmt/user_session.c b/fs/smb/server/mgmt/user_session.c index 9dec4c2940bc..b36d0676dbe5 100644 --- a/fs/smb/server/mgmt/user_session.c +++ b/fs/smb/server/mgmt/user_session.c @@ -104,29 +104,32 @@ int ksmbd_session_rpc_open(struct ksmbd_session *sess, char *rpc_name) if (!entry) return -ENOMEM; - down_read(&sess->rpc_lock); entry->method = method; entry->id = id = ksmbd_ipc_id_alloc(); if (id < 0) goto free_entry; + + down_write(&sess->rpc_lock); old = xa_store(&sess->rpc_handle_list, id, entry, KSMBD_DEFAULT_GFP); - if (xa_is_err(old)) + if (xa_is_err(old)) { + up_write(&sess->rpc_lock); goto free_id; + } resp = ksmbd_rpc_open(sess, id); - if (!resp) - goto erase_xa; + if (!resp) { + xa_erase(&sess->rpc_handle_list, entry->id); + up_write(&sess->rpc_lock); + goto free_id; + } - up_read(&sess->rpc_lock); + up_write(&sess->rpc_lock); kvfree(resp); return id; -erase_xa: - xa_erase(&sess->rpc_handle_list, entry->id); free_id: ksmbd_rpc_id_free(entry->id); free_entry: kfree(entry); - up_read(&sess->rpc_lock); return -EINVAL; } @@ -144,9 +147,14 @@ void ksmbd_session_rpc_close(struct ksmbd_session *sess, int id) int ksmbd_session_rpc_method(struct ksmbd_session *sess, int id) { struct ksmbd_session_rpc *entry; + int method; + down_read(&sess->rpc_lock); entry = xa_load(&sess->rpc_handle_list, id); - return entry ? entry->method : 0; + method = entry ? entry->method : 0; + up_read(&sess->rpc_lock); + + return method; } void ksmbd_session_destroy(struct ksmbd_session *sess)