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 385A830AAD2; Mon, 13 Oct 2025 15:17:43 +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=1760368664; cv=none; b=L5qAtOdPaPz45EZBU9DpQXofLzCYH4BbG11XGxCE7cfBOuf2v1kjrbdifgpMg9QwCjVVrkJfiGPgmpFGYrlUJZXCI6ube7R8gnhzVkGRI2vN1bXlzWjaxPAiLlUNn5kEPDrAi8lgW9eCDQfNiG5TUhsTc/D2TB1Jr5nZ4mq89C0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760368664; c=relaxed/simple; bh=0YZYuMZRTqljUxQV1k7DjQ8FTs/muD1Q2hdZX7GxBIc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ONKL+dIIqmoInbzXmwXRXNY8S4oRPbZ4Y9FgBHlVH+aWhJkyYp92BbF9Ttg3RCfKunqSfvhHxjqfRg/uQ3RnnScqD8s9wrC0nrlUPGEeEiJDUrQKJCigoKS2EUHhCju9EiI9u6Bxu0qZNyoZYs51ufylFAGONFqxA8f3rn/3V3s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=J2gipGxC; 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="J2gipGxC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 67F52C4CEE7; Mon, 13 Oct 2025 15:17:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1760368663; bh=0YZYuMZRTqljUxQV1k7DjQ8FTs/muD1Q2hdZX7GxBIc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=J2gipGxCtY9v6veDFFRJSlgy3HR5ILVrZgQog3F/TMzdhSY5i2DQKHOTpzqxqiADG Fh+B+R2CTFsnisvZFO/Zjd4gC+fnUnkQUx6pAp8X5hG7wBc8MylO2SXewPOXUHV9Cs wW6eSahLT/6scj7C+DV9wU3VgSSdjh1zrhZz2Q84= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yunseong Kim , Namjae Jeon , Steve French Subject: [PATCH 6.12 239/262] ksmbd: Fix race condition in RPC handle list access Date: Mon, 13 Oct 2025 16:46:21 +0200 Message-ID: <20251013144334.846356604@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251013144326.116493600@linuxfoundation.org> References: <20251013144326.116493600@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yunseong Kim commit 305853cce379407090a73b38c5de5ba748893aee upstream. 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 Signed-off-by: Greg Kroah-Hartman --- fs/smb/server/mgmt/user_session.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) --- 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_ 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 ksmb 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)