From 39d5330bc6de7937bd046405598b5c4f74ccd0d8 Mon Sep 17 00:00:00 2001 From: Henrique Carvalho Date: Thu, 5 Feb 2026 07:06:43 +0800 Subject: [PATCH 1/2] smb: server: fix leak of active_num_conn in ksmbd_tcp_new_connection() ANBZ: #34323 commit 787769c8cc50416af7b8b1a36e6bcd6aaa7680aa stable. commit 77ffbcac4e569566d0092d5f22627dfc0896b553 upstream. On kthread_run() failure in ksmbd_tcp_new_connection(), the transport is freed via free_transport(), which does not decrement active_num_conn, leaking this counter. Replace free_transport() with ksmbd_tcp_disconnect(). Fixes: 0d0d4680db22e ("ksmbd: add max connections parameter") Cc: stable@vger.kernel.org Signed-off-by: Henrique Carvalho Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman Fixes: CVE-2026-31711 Assisted-by: PatchPilot Signed-off-by: Ferry Meng --- fs/smb/server/transport_tcp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/smb/server/transport_tcp.c b/fs/smb/server/transport_tcp.c index 53c536f2ce9f..1437110d9277 100644 --- a/fs/smb/server/transport_tcp.c +++ b/fs/smb/server/transport_tcp.c @@ -41,6 +41,7 @@ static struct ksmbd_transport_ops ksmbd_tcp_transport_ops; static void tcp_stop_kthread(struct task_struct *kthread); static struct interface *alloc_iface(char *ifname); +static void ksmbd_tcp_disconnect(struct ksmbd_transport *t); #define KSMBD_TRANS(t) (&(t)->transport) #define TCP_TRANS(t) ((struct tcp_transport *)container_of(t, \ @@ -219,7 +220,7 @@ static int ksmbd_tcp_new_connection(struct socket *client_sk) if (IS_ERR(handler)) { pr_err("cannot start conn thread\n"); rc = PTR_ERR(handler); - free_transport(t); + ksmbd_tcp_disconnect(KSMBD_TRANS(t)); } return rc; -- Gitee From 7251bf4eaa65f3a500f36a1bd9c4cb669574908b Mon Sep 17 00:00:00 2001 From: Michael Bommarito Date: Wed, 15 Apr 2026 06:54:38 +0800 Subject: [PATCH 2/2] smb: server: fix active_num_conn leak on transport allocation failure ANBZ: #34323 commit 97f8d2648ef4871e4cd335e2d769cb40054a6772 stable. commit 6551300dc452ac16a855a83dbd1e74899542d3b3 upstream. Commit 77ffbcac4e56 ("smb: server: fix leak of active_num_conn in ksmbd_tcp_new_connection()") addressed the kthread_run() failure path. The earlier alloc_transport() == NULL path in the same function has the same leak, is reachable pre-authentication via any TCP connect to port 445, and was empirically reproduced on UML (ARCH=um, v7.0-rc7): a small number of forced allocation failures were sufficient to put ksmbd into a state where every subsequent connection attempt was rejected for the remainder of the boot. ksmbd_kthread_fn() increments active_num_conn before calling ksmbd_tcp_new_connection() and discards the return value, so when alloc_transport() returns NULL the socket is released and -ENOMEM returned without decrementing the counter. Each such failure permanently consumes one slot from the max_connections pool; once cumulative failures reach the cap, atomic_inc_return() hits the threshold on every subsequent accept and every new connection is rejected. The counter is only reset by module reload. An unauthenticated remote attacker can drive the server toward the memory pressure that makes alloc_transport() fail by holding open connections with large RFC1002 lengths up to MAX_STREAM_PROT_LEN (0x00FFFFFF); natural transient allocation failures on a loaded host produce the same drift more slowly. Mirror the existing rollback pattern in ksmbd_kthread_fn(): on the alloc_transport() failure path, decrement active_num_conn gated on server_conf.max_connections. Repro details: with the patch reverted, forced alloc_transport() NULL returns leaked counter slots and subsequent connection attempts -- including legitimate connects issued after the forced-fail window had closed -- were all rejected with "Limit the maximum number of connections". With this patch applied, the same connect sequence produces no rejections and the counter cycles cleanly between zero and one on every accept. Fixes: 0d0d4680db22 ("ksmbd: add max connections parameter") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-6 Assisted-by: Codex:gpt-5-4 Signed-off-by: Michael Bommarito Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman Fixes: CVE-2026-31711 Assisted-by: PatchPilot Signed-off-by: Ferry Meng --- fs/smb/server/transport_tcp.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/smb/server/transport_tcp.c b/fs/smb/server/transport_tcp.c index 1437110d9277..355af60b4bd3 100644 --- a/fs/smb/server/transport_tcp.c +++ b/fs/smb/server/transport_tcp.c @@ -203,6 +203,8 @@ static int ksmbd_tcp_new_connection(struct socket *client_sk) t = alloc_transport(client_sk); if (!t) { sock_release(client_sk); + if (server_conf.max_connections) + atomic_dec(&active_num_conn); return -ENOMEM; } -- Gitee