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 0C96E2288E3; Sat, 6 Dec 2025 14:02:56 +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=1765029777; cv=none; b=sBKhg0QD5C+urD/kco+RmnpE9RcSyIsRqqFUxL9IjAo5v/NmvnOIopzG62U08jrOZoOi5bBaNW3KyAcdtdA/ApqYzCeZg2mTxDQDeFE447SqHxvl0cbtUCsK+sdJXNjfxzRxUXVbL1YgpecmyG8Fg7/+BwV1iLTvr3HrhiHBUsI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765029777; c=relaxed/simple; bh=FQeuqPZ9ZuYejyixETsTXE9N5BCqnipWuGOsKpQT8/s=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=q6is65XVBIjGoZdUwpYi60IPkf5VxcF3kKqtBlV/ptgx3hkZvjHjSjWmBzZh6dWMu8clnS46eYbDSCnFT2vvZpd6P85JaqpUJr/ZYCznWHkOXSW/zZyrPhjbGUhXMoTin5e1LTKT0HwczarWtrcQuOSnmkHa+KKj4AO1FA7aC+o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Tq1NrON2; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Tq1NrON2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A3CA7C4CEF5; Sat, 6 Dec 2025 14:02:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765029776; bh=FQeuqPZ9ZuYejyixETsTXE9N5BCqnipWuGOsKpQT8/s=; h=From:To:Cc:Subject:Date:From; b=Tq1NrON2BZP0O0neJ54/wZ0R6J73Ah1ADobrL070YVk57oH2OdTL3FoU7BF1RyEi2 BtsCWZCT3pf+LRen+JVNfCt6Co/Xa9h9iizCa6c3GoSL211xE4+w1JLU84N6sib3f5 vOsP30z99qVodDXN+iEOad5TDNoEnQllRvgyx1jGR4DVXWpFZ2RtdBUqryEtPvSMuH Qo9wPQOpUPB9AqxABRXBKg0mxquPuHgkQvcENr4LDBQ1v3iGCknWeFjtzBx2bVWsGb 6q2axIdiyNUQ4GjhtJSw/ardcNhJShQVl+Yg2p/xbSOU0JNp15hAWVrwDTb0es00gz etUcfIp9rMjjw== From: Sasha Levin To: patches@lists.linux.dev, stable@vger.kernel.org Cc: Namjae Jeon , Qianchang Zhao , Zhitong Liu , Steve French , Sasha Levin , smfrench@gmail.com, alexandre.f.demers@gmail.com, alexander.deucher@amd.com, linux-cifs@vger.kernel.org Subject: [PATCH AUTOSEL 6.18-6.1] ksmbd: fix use-after-free in ksmbd_tree_connect_put under concurrency Date: Sat, 6 Dec 2025 09:02:06 -0500 Message-ID: <20251206140252.645973-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-cifs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.18 Content-Transfer-Encoding: 8bit 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: Sasha Levin --- LLM Generated explanations, may be completely bogus: fs/smb/server/mgmt/tree_connect.c | 18 ++++-------------- fs/smb/server/mgmt/tree_connect.h | 1 - fs/smb/server/smb2pdu.c | 3 --- 3 files changed, 4 insertions(+), 18 deletions(-) diff --git a/fs/smb/server/mgmt/tree_connect.c b/fs/smb/server/mgmt/tree_connect.c index ecfc575086712..d3483d9c757c7 100644 --- a/fs/smb/server/mgmt/tree_connect.c +++ b/fs/smb/server/mgmt/tree_connect.c @@ -78,7 +78,6 @@ ksmbd_tree_conn_connect(struct ksmbd_work *work, const char *share_name) tree_conn->t_state = TREE_NEW; status.tree_conn = tree_conn; atomic_set(&tree_conn->refcount, 1); - init_waitqueue_head(&tree_conn->refcount_q); ret = xa_err(xa_store(&sess->tree_conns, tree_conn->id, tree_conn, KSMBD_DEFAULT_GFP)); @@ -100,14 +99,8 @@ ksmbd_tree_conn_connect(struct ksmbd_work *work, const char *share_name) 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); } int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess, @@ -119,14 +112,11 @@ int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess, xa_erase(&sess->tree_conns, tree_conn->id); write_unlock(&sess->tree_conns_lock); - if (!atomic_dec_and_test(&tree_conn->refcount)) - wait_event(tree_conn->refcount_q, - atomic_read(&tree_conn->refcount) == 0); - ret = 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; } diff --git a/fs/smb/server/mgmt/tree_connect.h b/fs/smb/server/mgmt/tree_connect.h index a42cdd0510411..f0023d86716f2 100644 --- a/fs/smb/server/mgmt/tree_connect.h +++ b/fs/smb/server/mgmt/tree_connect.h @@ -33,7 +33,6 @@ struct ksmbd_tree_connect { int maximal_access; bool posix_extensions; atomic_t refcount; - wait_queue_head_t refcount_q; unsigned int t_state; }; diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index a2830ec67e782..dba29881debdc 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -2200,7 +2200,6 @@ int smb2_tree_disconnect(struct ksmbd_work *work) goto err_out; } - WARN_ON_ONCE(atomic_dec_and_test(&tcon->refcount)); tcon->t_state = TREE_DISCONNECTED; write_unlock(&sess->tree_conns_lock); @@ -2210,8 +2209,6 @@ int smb2_tree_disconnect(struct ksmbd_work *work) goto err_out; } - work->tcon = NULL; - rsp->StructureSize = cpu_to_le16(4); err = ksmbd_iov_pin_rsp(work, rsp, sizeof(struct smb2_tree_disconnect_rsp)); -- 2.51.0