[PATCH 1/6] usbip: fix stub_dev to check for stream socket

[PATCH 1/6] usbip: fix stub_dev to check for stream socket

[Shuah Khan]

Fix usbip_sockfd_store() to validate the passed in file descriptor is
a stream socket. If the file descriptor passed was a SOCK_DGRAM socket,
sock_recvmsg() can't detect end of stream.

Cc: stable@vger.kernel.org
Suggested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/usb/usbip/stub_dev.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/usbip/stub_dev.c b/drivers/usb/usbip/stub_dev.c
index 2305d425e6c9..90c105469a07 100644
--- a/drivers/usb/usbip/stub_dev.c
+++ b/drivers/usb/usbip/stub_dev.c
@@ -69,8 +69,16 @@ static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *a
 		}
 
 		socket = sockfd_lookup(sockfd, &err);
-		if (!socket)
+		if (!socket) {
+			dev_err(dev, "failed to lookup sock");
 			goto err;
+		}
+
+		if (socket->type != SOCK_STREAM) {
+			dev_err(dev, "Expecting SOCK_STREAM - found %d",
+				socket->type);
+			goto sock_err;
+		}
 
 		sdev->ud.tcp_socket = socket;
 		sdev->ud.sockfd = sockfd;
@@ -100,6 +108,8 @@ static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *a
 
 	return count;
 
+sock_err:
+	sockfd_put(socket);
 err:
 	spin_unlock_irq(&sdev->ud.lock);
 	return -EINVAL;
-- 
2.27.0

[PATCH 2/6] usbip: fix vhci_hcd to check for stream socket

[Shuah Khan]

Fix attach_store() to validate the passed in file descriptor is a
stream socket. If the file descriptor passed was a SOCK_DGRAM socket,
sock_recvmsg() can't detect end of stream.

Cc: stable@vger.kernel.org
Suggested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/usb/usbip/vhci_sysfs.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index 96e5371dc335..1e1ae9bd06ab 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -349,8 +349,16 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
 
 	/* Extract socket from fd. */
 	socket = sockfd_lookup(sockfd, &err);
-	if (!socket)
+	if (!socket) {
+		dev_err(dev, "failed to lookup sock");
 		return -EINVAL;
+	}
+	if (socket->type != SOCK_STREAM) {
+		dev_err(dev, "Expecting SOCK_STREAM - found %d",
+			socket->type);
+		sockfd_put(socket);
+		return -EINVAL;
+	}
 
 	/* now need lock until setting vdev status as used */
 
-- 
2.27.0

[PATCH 3/6] usbip: fix vudc to check for stream socket

[Shuah Khan]

Fix usbip_sockfd_store() to validate the passed in file descriptor is
a stream socket. If the file descriptor passed was a SOCK_DGRAM socket,
sock_recvmsg() can't detect end of stream.

Cc: stable@vger.kernel.org
Suggested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/usb/usbip/vudc_sysfs.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/usb/usbip/vudc_sysfs.c b/drivers/usb/usbip/vudc_sysfs.c
index 100f680c572a..83a0c59a3de8 100644
--- a/drivers/usb/usbip/vudc_sysfs.c
+++ b/drivers/usb/usbip/vudc_sysfs.c
@@ -138,6 +138,13 @@ static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *a
 			goto unlock_ud;
 		}
 
+		if (socket->type != SOCK_STREAM) {
+			dev_err(dev, "Expecting SOCK_STREAM - found %d",
+				socket->type);
+			ret = -EINVAL;
+			goto sock_err;
+		}
+
 		udc->ud.tcp_socket = socket;
 
 		spin_unlock_irq(&udc->ud.lock);
@@ -177,6 +184,8 @@ static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *a
 
 	return count;
 
+sock_err:
+	sockfd_put(socket);
 unlock_ud:
 	spin_unlock_irq(&udc->ud.lock);
 unlock:
-- 
2.27.0

[PATCH 4/6] usbip: fix stub_dev usbip_sockfd_store() races leading to gpf

[Shuah Khan]

usbip_sockfd_store() is invoked when user requests attach (import)
detach (unimport) usb device from usbip host. vhci_hcd sends import
request and usbip_sockfd_store() exports the device if it is free
for export.

Export and unexport are governed by local state and shared state
- Shared state (usbip device status, sockfd) - sockfd and Device
  status are used to determine if stub should be brought up or shut
  down.
- Local state (tcp_socket, rx and tx thread task_struct ptrs)
  A valid tcp_socket controls rx and tx thread operations while the
  device is in exported state.
- While the device is exported, device status is marked used and socket,
  sockfd, and thread pointers are valid.

Export sequence (stub-up) includes validating the socket and creating
receive (rx) and transmit (tx) threads to talk to the client to provide
access to the exported device. rx and tx threads depends on local and
shared state to be correct and in sync.

Unexport (stub-down) sequence shuts the socket down and stops the rx and
tx threads. Stub-down sequence relies on local and shared states to be
in sync.

There are races in updating the local and shared status in the current
stub-up sequence resulting in crashes. These stem from starting rx and
tx threads before local and global state is updated correctly to be in
sync.

1. Doesn't handle kthread_create() error and saves invalid ptr in local
   state that drives rx and tx threads.
2. Updates tcp_socket and sockfd,  starts stub_rx and stub_tx threads
   before updating usbip_device status to SDEV_ST_USED. This opens up a
   race condition between the threads and usbip_sockfd_store() stub up
   and down handling.

Fix the above problems:
- Stop using kthread_get_run() macro to create/start threads.
- Create threads and get task struct reference.
- Add kthread_create() failure handling and bail out.
- Hold usbip_device lock to update local and shared states after
  creating rx and tx threads.
- Update usbip_device status to SDEV_ST_USED.
- Update usbip_device tcp_socket, sockfd, tcp_rx, and tcp_tx
- Start threads after usbip_device (tcp_socket, sockfd, tcp_rx, tcp_tx,
  and status) is complete.

Credit goes to syzbot and Tetsuo Handa for finding and root-causing the
kthread_get_run() improper error handling problem and others. This is a
hard problem to find and debug since the races aren't seen in a normal
case. Fuzzing forces the race window to be small enough for the
kthread_get_run() error path bug and starting threads before updating the
local and shared state bug in the stub-up sequence.

Tested with syzbot reproducer:
- https://syzkaller.appspot.com/text?tag=ReproC&x=14801034d00000

Reported-by: syzbot <syzbot+a93fba6d384346a761e3@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+bf1a360e305ee719e364@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+95ce4b142579611ef0a9@syzkaller.appspotmail.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 9720b4bc76a83807 ("staging/usbip: convert to kthread")
Cc: stable@vger.kernel.org
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/usb/usbip/stub_dev.c | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/usbip/stub_dev.c b/drivers/usb/usbip/stub_dev.c
index 90c105469a07..8f1de1fbbeed 100644
--- a/drivers/usb/usbip/stub_dev.c
+++ b/drivers/usb/usbip/stub_dev.c
@@ -46,6 +46,8 @@ static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *a
 	int sockfd = 0;
 	struct socket *socket;
 	int rv;
+	struct task_struct *tcp_rx = NULL;
+	struct task_struct *tcp_tx = NULL;
 
 	if (!sdev) {
 		dev_err(dev, "sdev is null\n");
@@ -80,20 +82,36 @@ static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *a
 			goto sock_err;
 		}
 
-		sdev->ud.tcp_socket = socket;
-		sdev->ud.sockfd = sockfd;
-
+		/* unlock and create threads and get tasks */
 		spin_unlock_irq(&sdev->ud.lock);
+		tcp_rx = kthread_create(stub_rx_loop, &sdev->ud, "stub_rx");
+		if (IS_ERR(tcp_rx)) {
+			sockfd_put(socket);
+			return -EINVAL;
+		}
+		tcp_tx = kthread_create(stub_tx_loop, &sdev->ud, "stub_tx");
+		if (IS_ERR(tcp_tx)) {
+			kthread_stop(tcp_rx);
+			sockfd_put(socket);
+			return -EINVAL;
+		}
 
-		sdev->ud.tcp_rx = kthread_get_run(stub_rx_loop, &sdev->ud,
-						  "stub_rx");
-		sdev->ud.tcp_tx = kthread_get_run(stub_tx_loop, &sdev->ud,
-						  "stub_tx");
+		/* get task structs now */
+		get_task_struct(tcp_rx);
+		get_task_struct(tcp_tx);
 
+		/* lock and update sdev->ud state */
 		spin_lock_irq(&sdev->ud.lock);
+		sdev->ud.tcp_socket = socket;
+		sdev->ud.sockfd = sockfd;
+		sdev->ud.tcp_rx = tcp_rx;
+		sdev->ud.tcp_tx = tcp_tx;
 		sdev->ud.status = SDEV_ST_USED;
 		spin_unlock_irq(&sdev->ud.lock);
 
+		wake_up_process(sdev->ud.tcp_rx);
+		wake_up_process(sdev->ud.tcp_tx);
+
 	} else {
 		dev_info(dev, "stub down\n");
 
-- 
2.27.0

[PATCH 5/6] usbip: fix vhci_hcd attach_store() races leading to gpf

[Shuah Khan]

attach_store() is invoked when user requests import (attach) a device
from usbip host.

Attach and detach are governed by local state and shared state
- Shared state (usbip device status) - Device status is used to manage
  the attach and detach operations on import-able devices.
- Local state (tcp_socket, rx and tx thread task_struct ptrs)
  A valid tcp_socket controls rx and tx thread operations while the
  device is in exported state.
- Device has to be in the right state to be attached and detached.

Attach sequence includes validating the socket and creating receive (rx)
and transmit (tx) threads to talk to the host to get access to the
imported device. rx and tx threads depends on local and shared state to
be correct and in sync.

Detach sequence shuts the socket down and stops the rx and tx threads.
Detach sequence relies on local and shared states to be in sync.

There are races in updating the local and shared status in the current
attach sequence resulting in crashes. These stem from starting rx and
tx threads before local and global state is updated correctly to be in
sync.

1. Doesn't handle kthread_create() error and saves invalid ptr in local
   state that drives rx and tx threads.
2. Updates tcp_socket and sockfd,  starts stub_rx and stub_tx threads
   before updating usbip_device status to VDEV_ST_NOTASSIGNED. This opens
   up a race condition between the threads, port connect, and detach
   handling.

Fix the above problems:
- Stop using kthread_get_run() macro to create/start threads.
- Create threads and get task struct reference.
- Add kthread_create() failure handling and bail out.
- Hold vhci and usbip_device locks to update local and shared states after
  creating rx and tx threads.
- Update usbip_device status to VDEV_ST_NOTASSIGNED.
- Update usbip_device tcp_socket, sockfd, tcp_rx, and tcp_tx
- Start threads after usbip_device (tcp_socket, sockfd, tcp_rx, tcp_tx,
  and status) is complete.

Credit goes to syzbot and Tetsuo Handa for finding and root-causing the
kthread_get_run() improper error handling problem and others. This is
hard problem to find and debug since the races aren't seen in a normal
case. Fuzzing forces the race window to be small enough for the
kthread_get_run() error path bug and starting threads before updating the
local and shared state bug in the attach sequence.
- Update usbip_device tcp_rx and tcp_tx pointers holding vhci and
  usbip_device locks.

Tested with syzbot reproducer:
- https://syzkaller.appspot.com/text?tag=ReproC&x=14801034d00000

Reported-by: syzbot <syzbot+a93fba6d384346a761e3@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+bf1a360e305ee719e364@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+95ce4b142579611ef0a9@syzkaller.appspotmail.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 9720b4bc76a83807 ("staging/usbip: convert to kthread")
Cc: stable@vger.kernel.org
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/usb/usbip/vhci_sysfs.c | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index 1e1ae9bd06ab..c4b4256e5dad 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -312,6 +312,8 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
 	struct vhci *vhci;
 	int err;
 	unsigned long flags;
+	struct task_struct *tcp_rx = NULL;
+	struct task_struct *tcp_tx = NULL;
 
 	/*
 	 * @rhport: port number of vhci_hcd
@@ -360,9 +362,24 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
 		return -EINVAL;
 	}
 
-	/* now need lock until setting vdev status as used */
+	/* create threads before locking */
+	tcp_rx = kthread_create(vhci_rx_loop, &vdev->ud, "vhci_rx");
+	if (IS_ERR(tcp_rx)) {
+		sockfd_put(socket);
+		return -EINVAL;
+	}
+	tcp_tx = kthread_create(vhci_tx_loop, &vdev->ud, "vhci_tx");
+	if (IS_ERR(tcp_tx)) {
+		kthread_stop(tcp_rx);
+		sockfd_put(socket);
+		return -EINVAL;
+	}
+
+	/* get task structs now */
+	get_task_struct(tcp_rx);
+	get_task_struct(tcp_tx);
 
-	/* begin a lock */
+	/* now begin lock until setting vdev status set */
 	spin_lock_irqsave(&vhci->lock, flags);
 	spin_lock(&vdev->ud.lock);
 
@@ -372,6 +389,8 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
 		spin_unlock_irqrestore(&vhci->lock, flags);
 
 		sockfd_put(socket);
+		kthread_stop_put(tcp_rx);
+		kthread_stop_put(tcp_tx);
 
 		dev_err(dev, "port %d already used\n", rhport);
 		/*
@@ -390,6 +409,8 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
 	vdev->speed         = speed;
 	vdev->ud.sockfd     = sockfd;
 	vdev->ud.tcp_socket = socket;
+	vdev->ud.tcp_rx     = tcp_rx;
+	vdev->ud.tcp_tx     = tcp_tx;
 	vdev->ud.status     = VDEV_ST_NOTASSIGNED;
 	usbip_kcov_handle_init(&vdev->ud);
 
@@ -397,8 +418,8 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
 	spin_unlock_irqrestore(&vhci->lock, flags);
 	/* end the lock */
 
-	vdev->ud.tcp_rx = kthread_get_run(vhci_rx_loop, &vdev->ud, "vhci_rx");
-	vdev->ud.tcp_tx = kthread_get_run(vhci_tx_loop, &vdev->ud, "vhci_tx");
+	wake_up_process(vdev->ud.tcp_rx);
+	wake_up_process(vdev->ud.tcp_tx);
 
 	rh_port_connect(vdev, speed);
 
-- 
2.27.0

[PATCH 6/6] usbip: fix vudc usbip_sockfd_store races leading to gpf

[Shuah Khan]

usbip_sockfd_store() is invoked when user requests attach (import)
detach (unimport) usb gadget device from usbip host. vhci_hcd sends
import request and usbip_sockfd_store() exports the device if it is
free for export.

Export and unexport are governed by local state and shared state
- Shared state (usbip device status, sockfd) - sockfd and Device
  status are used to determine if stub should be brought up or shut
  down. Device status is shared between host and client.
- Local state (tcp_socket, rx and tx thread task_struct ptrs)
  A valid tcp_socket controls rx and tx thread operations while the
  device is in exported state.
- While the device is exported, device status is marked used and socket,
  sockfd, and thread pointers are valid.

Export sequence (stub-up) includes validating the socket and creating
receive (rx) and transmit (tx) threads to talk to the client to provide
access to the exported device. rx and tx threads depends on local and
shared state to be correct and in sync.

Unexport (stub-down) sequence shuts the socket down and stops the rx and
tx threads. Stub-down sequence relies on local and shared states to be
in sync.

There are races in updating the local and shared status in the current
stub-up sequence resulting in crashes. These stem from starting rx and
tx threads before local and global state is updated correctly to be in
sync.

1. Doesn't handle kthread_create() error and saves invalid ptr in local
   state that drives rx and tx threads.
2. Updates tcp_socket and sockfd,  starts stub_rx and stub_tx threads
   before updating usbip_device status to SDEV_ST_USED. This opens up a
   race condition between the threads and usbip_sockfd_store() stub up
   and down handling.

Fix the above problems:
- Stop using kthread_get_run() macro to create/start threads.
- Create threads and get task struct reference.
- Add kthread_create() failure handling and bail out.
- Hold usbip_device lock to update local and shared states after
  creating rx and tx threads.
- Update usbip_device status to SDEV_ST_USED.
- Update usbip_device tcp_socket, sockfd, tcp_rx, and tcp_tx
- Start threads after usbip_device (tcp_socket, sockfd, tcp_rx, tcp_tx,
  and status) is complete.

Credit goes to syzbot and Tetsuo Handa for finding and root-causing the
kthread_get_run() improper error handling problem and others. This is a
hard problem to find and debug since the races aren't seen in a normal
case. Fuzzing forces the race window to be small enough for the
kthread_get_run() error path bug and starting threads before updating the
local and shared state bug in the stub-up sequence.

Reported-by: syzbot <syzbot+a93fba6d384346a761e3@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+bf1a360e305ee719e364@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+95ce4b142579611ef0a9@syzkaller.appspotmail.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 9720b4bc76a83807 ("staging/usbip: convert to kthread")
Cc: stable@vger.kernel.org
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/usb/usbip/vudc_sysfs.c | 42 +++++++++++++++++++++++++++-------
 1 file changed, 34 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/usbip/vudc_sysfs.c b/drivers/usb/usbip/vudc_sysfs.c
index 83a0c59a3de8..a3ec39fc6177 100644
--- a/drivers/usb/usbip/vudc_sysfs.c
+++ b/drivers/usb/usbip/vudc_sysfs.c
@@ -90,8 +90,9 @@ static ssize_t dev_desc_read(struct file *file, struct kobject *kobj,
 }
 static BIN_ATTR_RO(dev_desc, sizeof(struct usb_device_descriptor));
 
-static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *attr,
-		     const char *in, size_t count)
+static ssize_t usbip_sockfd_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *in, size_t count)
 {
 	struct vudc *udc = (struct vudc *) dev_get_drvdata(dev);
 	int rv;
@@ -100,6 +101,8 @@ static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *a
 	struct socket *socket;
 	unsigned long flags;
 	int ret;
+	struct task_struct *tcp_rx = NULL;
+	struct task_struct *tcp_tx = NULL;
 
 	rv = kstrtoint(in, 0, &sockfd);
 	if (rv != 0)
@@ -145,24 +148,47 @@ static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *a
 			goto sock_err;
 		}
 
-		udc->ud.tcp_socket = socket;
-
+		/* unlock and create threads and get tasks */
 		spin_unlock_irq(&udc->ud.lock);
 		spin_unlock_irqrestore(&udc->lock, flags);
 
-		udc->ud.tcp_rx = kthread_get_run(&v_rx_loop,
-						    &udc->ud, "vudc_rx");
-		udc->ud.tcp_tx = kthread_get_run(&v_tx_loop,
-						    &udc->ud, "vudc_tx");
+		tcp_rx = kthread_create(&v_rx_loop, &udc->ud, "vudc_rx");
+		if (IS_ERR(tcp_rx)) {
+			sockfd_put(socket);
+			return -EINVAL;
+		}
+		tcp_tx = kthread_create(&v_tx_loop, &udc->ud, "vudc_tx");
+		if (IS_ERR(tcp_tx)) {
+			kthread_stop(tcp_rx);
+			sockfd_put(socket);
+			return -EINVAL;
+		}
+
+		/* get task structs now */
+		get_task_struct(tcp_rx);
+		get_task_struct(tcp_tx);
 
+		/* lock and update udc->ud state */
 		spin_lock_irqsave(&udc->lock, flags);
 		spin_lock_irq(&udc->ud.lock);
+
+		udc->ud.tcp_socket = socket;
+		udc->ud.tcp_rx = tcp_rx;
+		udc->ud.tcp_rx = tcp_tx;
 		udc->ud.status = SDEV_ST_USED;
+
 		spin_unlock_irq(&udc->ud.lock);
 
 		ktime_get_ts64(&udc->start_time);
 		v_start_timer(udc);
 		udc->connected = 1;
+
+		spin_unlock_irqrestore(&udc->lock, flags);
+
+		wake_up_process(udc->ud.tcp_rx);
+		wake_up_process(udc->ud.tcp_tx);
+		return count;
+
 	} else {
 		if (!udc->connected) {
 			dev_err(dev, "Device not connected");
-- 
2.27.0