From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 3AB3A559CB0 for ; Tue, 8 Sep 2026 13:37:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788874684; cv=none; b=ZzgiNs57nZnldk4gjZmrimboCxzTCHy3t1amcWuDDA+ZCVmGw52o7k+WdIUgKFdD9leCRtO9Ju9KHnMIpeWTq/NdBt786XzOsKVOHQIjNFqg8UijdCfs0hpkPHklLheEZ1GtXaX2SCB0deT0UxEIpwbt7nAjINv8PUFaWUdjtjA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788874684; c=relaxed/simple; bh=drxACqDPVbcTDx8woAFFkWjjV0MCMYh9SMqTqtue+vQ=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=U9Momsx25uokXsbBKVsnK07/lN/WM9gCNlYbYigWAOJFSk8p9KlqkLxYnW5DtUVnm9z/3acva/sryxgB8Tuh7T2GKKKfThkH/aaWJKSwxTNjXYpA8/9vcoupug0ZM7B4/dXAwjq64sgJ2gReK6R/UyUH9hDhv0gbGNDwIbCn3JA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=yXKMBKs0; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="yXKMBKs0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3687B1F00A3F; Tue, 8 Sep 2026 13:37:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788874668; bh=RV391Yd3jenCrVqKJJnpH8WFvrnByNJhQcTEdFe9gWg=; h=Subject:To:Cc:From:Date; b=yXKMBKs0rVF/oDPh9IE2OQ/KNMwPnhJQaSpmq2hokWKpjaB1QQr9SBgYXr0IB5Dik NtddA57AK6aa9ZRUHtipQ2G9Sk79iZYB4qQO7vRGuuW/fIZQNbMVjz+Op0Lj1czdbO IhOw9RX4BtTsLKaXO9rZdskQdeAev9eSihlCSOGQ= Subject: FAILED: patch "[PATCH] ksmbd: fix tree connection use-after-free in" failed to apply to 5.15-stable tree To: cenzhang@linux.microsoft.com,linkinjeon@kernel.org,xmei5@asu.edu Cc: From: Date: Tue, 08 Sep 2026 15:33:05 +0200 Message-ID: <2026090805-bodacious-unloaded-3010@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 5.15-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-5.15.y git checkout FETCH_HEAD git cherry-pick -x b5ec6c462aab1062cf5d1e667ba7c6442f737055 # git commit -s git send-email --to '' --in-reply-to '2026090805-bodacious-unloaded-3010@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From b5ec6c462aab1062cf5d1e667ba7c6442f737055 Mon Sep 17 00:00:00 2001 From: "Cen Zhang (Microsoft Security FORGE Labs)" Date: Tue, 1 Sep 2026 14:21:36 -0400 Subject: [PATCH] ksmbd: fix tree connection use-after-free in smb2_tree_connect() ksmbd_tree_conn_connect() publishes a new tree connection in sess->tree_conns with a single reference and returns its pointer to smb2_tree_connect(). The handler continues to initialize the object and build the response after publication. A concurrent session logoff can erase the connection and drop that reference, freeing the object while the handler still uses it. BUG: KASAN: slab-use-after-free in smb2_tree_connect+0xe3d/0xf90 smb2_tree_connect (fs/smb/server/smb2pdu.c:2872) handle_ksmbd_work process_one_work worker_thread kthread After xa_store() succeeds, take a second reference before releasing tree_conns_lock. The original reference belongs to the xarray entry and the second belongs to the creating smb2_tree_connect() handler. Keep the references balanced in every path: - On normal exit or an error after publication, smb2_tree_connect() drops its creator reference. Error cleanup also calls ksmbd_tree_conn_disconnect(), which drops the xarray reference only if it removes the exact entry. - SMB2 TREE_DISCONNECT uses the same helper to remove the entry and drop its xarray reference. The request's existing lookup reference remains owned by the request and is released by the existing cleanup. - Session LOGOFF removes each entry and drops its xarray reference. If it wins the race, later cleanup sees that the entry is gone and does not drop that reference again. To enforce this ownership, claim the disconnected state and erase the exact entry atomically under tree_conns_lock. This guarantees one drop for the xarray reference and one drop by each in-flight user, regardless of which teardown path wins. If logoff removes the entry before initialization completes, fail the connect instead of marking the detached object TREE_CONNECTED. Fixes: 33b235a6e6eb ("ksmbd: fix race condition between tree conn lookup and disconnect") Reported-by: Xiang Mei (Microsoft) Cc: AutonomousCodeSecurity@microsoft.com Cc: stable@vger.kernel.org Signed-off-by: Cen Zhang (Microsoft Security FORGE Labs) Signed-off-by: Namjae Jeon diff --git a/fs/smb/server/mgmt/tree_connect.c b/fs/smb/server/mgmt/tree_connect.c index 5f63e236267a..dd1db3554cae 100644 --- a/fs/smb/server/mgmt/tree_connect.c +++ b/fs/smb/server/mgmt/tree_connect.c @@ -82,6 +82,8 @@ ksmbd_tree_conn_connect(struct ksmbd_work *work, const char *share_name) down_write(&sess->tree_conns_lock); ret = xa_err(xa_store(&sess->tree_conns, tree_conn->id, tree_conn, KSMBD_DEFAULT_GFP)); + if (!ret) + atomic_inc(&tree_conn->refcount); up_write(&sess->tree_conns_lock); if (ret) { status.ret = -ENOMEM; @@ -129,6 +131,12 @@ int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess, struct ksmbd_tree_connect *tree_conn) { down_write(&sess->tree_conns_lock); + if (tree_conn->t_state == TREE_DISCONNECTED || + xa_load(&sess->tree_conns, tree_conn->id) != tree_conn) { + up_write(&sess->tree_conns_lock); + return -ENOENT; + } + tree_conn->t_state = TREE_DISCONNECTED; xa_erase(&sess->tree_conns, tree_conn->id); up_write(&sess->tree_conns_lock); diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index d656832d82ef..0ecc52fde69c 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -2790,6 +2790,7 @@ int smb2_tree_connect(struct ksmbd_work *work) struct ksmbd_session *sess = work->sess; char *treename = NULL, *name = NULL; struct ksmbd_tree_conn_status status; + struct ksmbd_tree_connect *tree_conn = NULL; struct ksmbd_share_config *share = NULL; int rc = -EINVAL; @@ -2817,6 +2818,7 @@ int smb2_tree_connect(struct ksmbd_work *work) status = ksmbd_tree_conn_connect(work, name); if (status.ret == KSMBD_TREE_CONN_STATUS_OK) { + tree_conn = status.tree_conn; rsp->hdr.Id.SyncId.TreeId = cpu_to_le32(status.tree_conn->id); share = status.tree_conn->share_conf; @@ -2860,8 +2862,15 @@ int smb2_tree_connect(struct ksmbd_work *work) status.tree_conn->posix_extensions = true; down_write(&sess->tree_conns_lock); - status.tree_conn->t_state = TREE_CONNECTED; + if (status.tree_conn->t_state == TREE_DISCONNECTED) { + status.ret = KSMBD_TREE_CONN_STATUS_ERROR; + share = NULL; + } else { + status.tree_conn->t_state = TREE_CONNECTED; + } up_write(&sess->tree_conns_lock); + if (status.ret != KSMBD_TREE_CONN_STATUS_OK) + goto out_err1; rsp->StructureSize = cpu_to_le16(16); out_err1: /* @@ -2888,9 +2897,6 @@ int smb2_tree_connect(struct ksmbd_work *work) rc = ksmbd_iov_pin_rsp(work, rsp, sizeof(struct smb2_tree_connect_rsp)); if (rc) { if (status.ret == KSMBD_TREE_CONN_STATUS_OK) { - down_write(&sess->tree_conns_lock); - status.tree_conn->t_state = TREE_DISCONNECTED; - up_write(&sess->tree_conns_lock); ksmbd_tree_conn_disconnect(sess, status.tree_conn); status.tree_conn = NULL; } @@ -2931,6 +2937,9 @@ int smb2_tree_connect(struct ksmbd_work *work) if (status.ret != KSMBD_TREE_CONN_STATUS_OK) smb2_set_err_rsp(work); + if (tree_conn) + ksmbd_tree_connect_put(tree_conn); + return rc; } @@ -3034,17 +3043,6 @@ int smb2_tree_disconnect(struct ksmbd_work *work) ksmbd_close_tree_conn_fds(work); - down_write(&sess->tree_conns_lock); - if (tcon->t_state == TREE_DISCONNECTED) { - up_write(&sess->tree_conns_lock); - rsp->hdr.Status = STATUS_NETWORK_NAME_DELETED; - err = -ENOENT; - goto err_out; - } - - tcon->t_state = TREE_DISCONNECTED; - up_write(&sess->tree_conns_lock); - err = ksmbd_tree_conn_disconnect(sess, tcon); if (err) { rsp->hdr.Status = STATUS_NETWORK_NAME_DELETED;