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Fri, 13 Mar 2026 10:17:20 -0700 (PDT) Received: from JooHJ-PC.localdomain ([121.65.54.92]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82a0727f2fcsm6330485b3a.28.2026.03.13.10.17.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Mar 2026 10:17:19 -0700 (PDT) From: Hyungjung Joo To: ericvh@kernel.org, lucho@ionkov.net, asmadeus@codewreck.org Cc: linux_oss@crudebyte.com, m.grzeschik@pengutronix.de, gregkh@linuxfoundation.org, v9fs@lists.linux.dev, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Hyungjung Joo Subject: [PATCH] net: 9p: usbg: clear stale client pointer on close Date: Sat, 14 Mar 2026 02:16:59 +0900 Message-Id: <20260313171659.1225180-1-jhj140711@gmail.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" p9_usbg_close() tears down the client transport, but usb9pfs keeps using usb9pfs->client from asynchronous TX and RX completion handlers. A late completion can therefore dereference a client that has already been freed during mount teardown. Clear usb9pfs->client under usb9pfs->lock when closing the transport, detach any pending TX request from in_req->context, and make the TX/RX completion handlers bail out once the transport has been detached. This keeps late completions from touching a freed or rebound p9_client. Fixes: a3be076dc174 ("net/9p/usbg: Add new usb gadget function transport") Cc: stable@vger.kernel.org Reviewed-by: Greg Kroah-Hartman Signed-off-by: Hyungjung Joo --- net/9p/trans_usbg.c | 63 +++++++++++++++++++++++++++++++++------------ 1 file changed, 47 insertions(+), 16 deletions(-) diff --git a/net/9p/trans_usbg.c b/net/9p/trans_usbg.c index 1ce70338999c..3c2aa1943f93 100644 --- a/net/9p/trans_usbg.c +++ b/net/9p/trans_usbg.c @@ -149,7 +149,8 @@ static void usb9pfs_tx_complete(struct usb_ep *ep, stru= ct usb_request *req) { struct f_usb9pfs *usb9pfs =3D ep->driver_data; struct usb_composite_dev *cdev =3D usb9pfs->function.config->cdev; - struct p9_req_t *p9_tx_req =3D req->context; + struct p9_client *client; + struct p9_req_t *p9_tx_req; unsigned long flags; =20 /* reset zero packages */ @@ -165,18 +166,27 @@ static void usb9pfs_tx_complete(struct usb_ep *ep, st= ruct usb_request *req) ep->name, req->status, req->actual, req->length); =20 spin_lock_irqsave(&usb9pfs->lock, flags); - WRITE_ONCE(p9_tx_req->status, REQ_STATUS_SENT); + client =3D usb9pfs->client; + p9_tx_req =3D req->context; + req->context =3D NULL; =20 - p9_req_put(usb9pfs->client, p9_tx_req); + if (!client || !p9_tx_req) { + spin_unlock_irqrestore(&usb9pfs->lock, flags); + complete(&usb9pfs->send); + return; + } =20 - req->context =3D NULL; + WRITE_ONCE(p9_tx_req->status, REQ_STATUS_SENT); + + p9_req_put(client, p9_tx_req); =20 spin_unlock_irqrestore(&usb9pfs->lock, flags); =20 complete(&usb9pfs->send); } =20 -static struct p9_req_t *usb9pfs_rx_header(struct f_usb9pfs *usb9pfs, void = *buf) +static struct p9_req_t *usb9pfs_rx_header(struct f_usb9pfs *usb9pfs, + struct p9_client *client, void *buf) { struct p9_req_t *p9_rx_req; struct p9_fcall rc; @@ -202,7 +212,7 @@ static struct p9_req_t *usb9pfs_rx_header(struct f_usb9= pfs *usb9pfs, void *buf) "mux %p pkt: size: %d bytes tag: %d\n", usb9pfs, rc.size, rc.tag); =20 - p9_rx_req =3D p9_tag_lookup(usb9pfs->client, rc.tag); + p9_rx_req =3D p9_tag_lookup(client, rc.tag); if (!p9_rx_req || p9_rx_req->status !=3D REQ_STATUS_SENT) { p9_debug(P9_DEBUG_ERROR, "Unexpected packet tag %d\n", rc.tag); return NULL; @@ -212,7 +222,7 @@ static struct p9_req_t *usb9pfs_rx_header(struct f_usb9= pfs *usb9pfs, void *buf) p9_debug(P9_DEBUG_ERROR, "requested packet size too big: %d for tag %d with capacity %zd\n", rc.size, rc.tag, p9_rx_req->rc.capacity); - p9_req_put(usb9pfs->client, p9_rx_req); + p9_req_put(client, p9_rx_req); return NULL; } =20 @@ -220,7 +230,7 @@ static struct p9_req_t *usb9pfs_rx_header(struct f_usb9= pfs *usb9pfs, void *buf) p9_debug(P9_DEBUG_ERROR, "No recv fcall for tag %d (req %p), disconnecting!\n", rc.tag, p9_rx_req); - p9_req_put(usb9pfs->client, p9_rx_req); + p9_req_put(client, p9_rx_req); return NULL; } =20 @@ -231,8 +241,10 @@ static void usb9pfs_rx_complete(struct usb_ep *ep, str= uct usb_request *req) { struct f_usb9pfs *usb9pfs =3D ep->driver_data; struct usb_composite_dev *cdev =3D usb9pfs->function.config->cdev; + struct p9_client *client; struct p9_req_t *p9_rx_req; unsigned int req_size =3D req->actual; + unsigned long flags; int status =3D REQ_STATUS_RCVD; =20 if (req->status) { @@ -241,9 +253,16 @@ static void usb9pfs_rx_complete(struct usb_ep *ep, str= uct usb_request *req) return; } =20 - p9_rx_req =3D usb9pfs_rx_header(usb9pfs, req->buf); - if (!p9_rx_req) + spin_lock_irqsave(&usb9pfs->lock, flags); + client =3D usb9pfs->client; + if (!client) { + spin_unlock_irqrestore(&usb9pfs->lock, flags); return; + } + + p9_rx_req =3D usb9pfs_rx_header(usb9pfs, client, req->buf); + if (!p9_rx_req) + goto out_unlock; =20 if (req_size > p9_rx_req->rc.capacity) { dev_err(&cdev->gadget->dev, @@ -257,8 +276,11 @@ static void usb9pfs_rx_complete(struct usb_ep *ep, str= uct usb_request *req) =20 p9_rx_req->rc.size =3D req_size; =20 - p9_client_cb(usb9pfs->client, p9_rx_req, status); - p9_req_put(usb9pfs->client, p9_rx_req); + p9_client_cb(client, p9_rx_req, status); + p9_req_put(client, p9_rx_req); + +out_unlock: + spin_unlock_irqrestore(&usb9pfs->lock, flags); =20 complete(&usb9pfs->received); } @@ -416,7 +438,9 @@ static int p9_usbg_create(struct p9_client *client, str= uct fs_context *fc) client->status =3D Disconnected; else client->status =3D Connected; + spin_lock_irq(&usb9pfs->lock); usb9pfs->client =3D client; + spin_unlock_irq(&usb9pfs->lock); =20 client->trans_mod->maxsize =3D usb9pfs->buflen; =20 @@ -427,18 +451,25 @@ static int p9_usbg_create(struct p9_client *client, s= truct fs_context *fc) =20 static void usb9pfs_clear_tx(struct f_usb9pfs *usb9pfs) { + struct p9_client *client; struct p9_req_t *req; + unsigned long flags; =20 - guard(spinlock_irqsave)(&usb9pfs->lock); + spin_lock_irqsave(&usb9pfs->lock, flags); + client =3D usb9pfs->client; + usb9pfs->client =3D NULL; + req =3D usb9pfs->in_req ? usb9pfs->in_req->context : NULL; + if (usb9pfs->in_req) + usb9pfs->in_req->context =3D NULL; + spin_unlock_irqrestore(&usb9pfs->lock, flags); =20 - req =3D usb9pfs->in_req->context; - if (!req) + if (!req || !client) return; =20 if (!req->t_err) req->t_err =3D -ECONNRESET; =20 - p9_client_cb(usb9pfs->client, req, REQ_STATUS_ERROR); + p9_client_cb(client, req, REQ_STATUS_ERROR); } =20 static void p9_usbg_close(struct p9_client *client) --=20 2.34.1