From nobody Sun Feb 8 15:30:59 2026 Received: from n169-111.mail.139.com (n169-111.mail.139.com [120.232.169.111]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0C74030DD01; Thu, 22 Jan 2026 03:46:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=120.232.169.111 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769053598; cv=none; b=nntF2HJUUG0ocuFV42fx8e7gABb73SlWHJNi5IoEZVkybMhp8Sl8Ikk2vIm20TVaEaKW2lS+xZnPcxWAcD5L6/eZzu3GFW9kzcY502SV3oQxM/fF88FTWQe7s5hyVHEQA5iBlsBrfiuBuGY9bhdUgq3Jeq/K2a1ZNUwvzkhJ5wg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769053598; c=relaxed/simple; bh=g744lz6iU9xFRdnsnHyyhaVQs6SpUU91JT0OadSyyg0=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=j90a5B0L9PhChCOn9q0WWxqQq58VNhXO5uk90cjbtagAHIB3cqIOWYA3VKS66bKln4mtATpWvK0wihRxX4c9vbQofUFJ+sLL6xR4Sitv9wPzmsCpomMZwLiWRrsQXyjdpcK6UPBZBFpXZg7cZD6sFwpy6qfnf+CBSspsbC+QCuM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=139.com; spf=pass smtp.mailfrom=139.com; dkim=pass (1024-bit key) header.d=139.com header.i=@139.com header.b=Iy5h1HxG; arc=none smtp.client-ip=120.232.169.111 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=139.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=139.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=139.com header.i=@139.com header.b="Iy5h1HxG" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=139.com; s=dkim; l=0; h=from:subject:message-id:to:cc:mime-version; bh=47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=; b=Iy5h1HxGWG96b8PvFjSXUudZazlxfy+k67BEtqx1SLvLNMIwNSLE27Mu5FU7NFR39rK78mLfFQMQU M240QSrWo0WKBdlNq4Z06D4BtH9iAnKrROWn4bcOEebTj8myglpK6tehOaw1fX5wEfIKpjMIVXElcl fQWW2TO4PmxwCLug= X-RM-TagInfo: emlType=0 X-RM-SPAM: X-RM-SPAM-FLAG: 00000000 Received: from NTT-kernel-dev (unknown[60.247.85.88]) by rmsmtp-lg-appmail-17-12016 (RichMail) with SMTP id 2ef069719c9511d-0a1eb; Thu, 22 Jan 2026 11:42:14 +0800 (CST) X-RM-TRANSID: 2ef069719c9511d-0a1eb From: Rajani Kantha <681739313@139.com> To: gregkh@linuxfoundation.org, stable@vger.kernel.org, linkinjeon@kernel.org Cc: patches@lists.linux.dev, linux-kernel@vger.kernel.org, senozhatsky@chromium.org, sfrench@samba.org, hyc.lee@gmail.com, linux-cifs@vger.kernel.org, pioooooooooip@gmail.com, liuzhitong1993@gmail.com, stfrench@microsoft.com Subject: [PATCH 5.15.y] ksmbd: fix use-after-free in ksmbd_tree_connect_put under concurrency Date: Thu, 22 Jan 2026 11:42:12 +0800 Message-Id: <20260122034212.3111671-1-681739313@139.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Namjae Jeon [ Upstream commit b39a1833cc4a2755b02603eec3a71a85e9dff926 ] Under high concurrency, A tree-connection object (tcon) is freed on a disconnect path while another path still holds a reference and later executes *_put()/write on it. Reported-by: Qianchang Zhao Reported-by: Zhitong Liu Signed-off-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Rajani Kantha <681739313@139.com> --- fs/ksmbd/mgmt/tree_connect.c | 18 ++++-------------- fs/ksmbd/mgmt/tree_connect.h | 1 - fs/ksmbd/smb2pdu.c | 3 --- 3 files changed, 4 insertions(+), 18 deletions(-) diff --git a/fs/ksmbd/mgmt/tree_connect.c b/fs/ksmbd/mgmt/tree_connect.c index d2c81a8a11dd..0b6847f04fcc 100644 --- a/fs/ksmbd/mgmt/tree_connect.c +++ b/fs/ksmbd/mgmt/tree_connect.c @@ -76,7 +76,6 @@ ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct k= smbd_session *sess, tree_conn->t_state =3D TREE_NEW; status.tree_conn =3D tree_conn; atomic_set(&tree_conn->refcount, 1); - init_waitqueue_head(&tree_conn->refcount_q); =20 ret =3D xa_err(xa_store(&sess->tree_conns, tree_conn->id, tree_conn, GFP_KERNEL)); @@ -98,14 +97,8 @@ ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct = ksmbd_session *sess, =20 void ksmbd_tree_connect_put(struct ksmbd_tree_connect *tcon) { - /* - * Checking waitqueue to releasing tree connect on - * tree disconnect. waitqueue_active is safe because it - * uses atomic operation for condition. - */ - if (!atomic_dec_return(&tcon->refcount) && - waitqueue_active(&tcon->refcount_q)) - wake_up(&tcon->refcount_q); + if (atomic_dec_and_test(&tcon->refcount)) + kfree(tcon); } =20 int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess, @@ -117,14 +110,11 @@ int ksmbd_tree_conn_disconnect(struct ksmbd_session *= sess, xa_erase(&sess->tree_conns, tree_conn->id); write_unlock(&sess->tree_conns_lock); =20 - if (!atomic_dec_and_test(&tree_conn->refcount)) - wait_event(tree_conn->refcount_q, - atomic_read(&tree_conn->refcount) =3D=3D 0); - ret =3D ksmbd_ipc_tree_disconnect_request(sess->id, tree_conn->id); ksmbd_release_tree_conn_id(sess, tree_conn->id); ksmbd_share_config_put(tree_conn->share_conf); - kfree(tree_conn); + if (atomic_dec_and_test(&tree_conn->refcount)) + kfree(tree_conn); return ret; } =20 diff --git a/fs/ksmbd/mgmt/tree_connect.h b/fs/ksmbd/mgmt/tree_connect.h index 6377a70b811c..bf47c3f65f03 100644 --- a/fs/ksmbd/mgmt/tree_connect.h +++ b/fs/ksmbd/mgmt/tree_connect.h @@ -32,7 +32,6 @@ struct ksmbd_tree_connect { int maximal_access; bool posix_extensions; atomic_t refcount; - wait_queue_head_t refcount_q; unsigned int t_state; }; =20 diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c index c0b5985701bf..b4a1aa1bc960 100644 --- a/fs/ksmbd/smb2pdu.c +++ b/fs/ksmbd/smb2pdu.c @@ -2169,7 +2169,6 @@ int smb2_tree_disconnect(struct ksmbd_work *work) goto err_out; } =20 - WARN_ON_ONCE(atomic_dec_and_test(&tcon->refcount)); tcon->t_state =3D TREE_DISCONNECTED; write_unlock(&sess->tree_conns_lock); =20 @@ -2179,8 +2178,6 @@ int smb2_tree_disconnect(struct ksmbd_work *work) goto err_out; } =20 - work->tcon =3D NULL; - rsp->StructureSize =3D cpu_to_le16(4); err =3D ksmbd_iov_pin_rsp(work, rsp, sizeof(struct smb2_tree_disconnect_rsp)); --=20 2.34.1