[PATCH 4.9 25/37] usbip: stub-dev synchronize sysfs code paths

Greg Kroah-Hartman
2021-04-26T07:33:40Z

From: Shuah Khan <skhan@linuxfoundation.org>

commit 9dbf34a834563dada91366c2ac266f32ff34641a upstream.

Fuzzing uncovered race condition between sysfs code paths in usbip
drivers. Device connect/disconnect code paths initiated through
sysfs interface are prone to races if disconnect happens during
connect and vice versa.

Use sysfs_lock to protect sysfs paths in stub-dev.

Cc: stable@vger.kernel.org # 4.9.x
Reported-and-tested-by: syzbot+a93fba6d384346a761e3@syzkaller.appspotmail.com
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/2b182f3561b4a065bf3bf6dce3b0e9944ba17b3f.1616807117.git.skhan@linuxfoundation.org
Signed-off-by: Tom Seewald <tseewald@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/usbip/stub_dev.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

--- a/drivers/usb/usbip/stub_dev.c
+++ b/drivers/usb/usbip/stub_dev.c
@@ -77,6 +77,7 @@ static ssize_t store_sockfd(struct devic

dev_info(dev, "stub up\n");

+ mutex_lock(&sdev->ud.sysfs_lock);
spin_lock_irq(&sdev->ud.lock);

if (sdev->ud.status != SDEV_ST_AVAILABLE) {
@@ -101,13 +102,13 @@ static ssize_t store_sockfd(struct devic
tcp_rx = kthread_create(stub_rx_loop, &sdev->ud, "stub_rx");
if (IS_ERR(tcp_rx)) {
sockfd_put(socket);
- return -EINVAL;
+ goto unlock_mutex;
}
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;
+ goto unlock_mutex;
}

/* get task structs now */
@@ -126,6 +127,8 @@ static ssize_t store_sockfd(struct devic
wake_up_process(sdev->ud.tcp_rx);
wake_up_process(sdev->ud.tcp_tx);

+ mutex_unlock(&sdev->ud.sysfs_lock);
+
} else {
dev_info(dev, "stub down\n");

@@ -136,6 +139,7 @@ static ssize_t store_sockfd(struct devic
spin_unlock_irq(&sdev->ud.lock);

usbip_event_add(&sdev->ud, SDEV_EVENT_DOWN);
+ mutex_unlock(&sdev->ud.sysfs_lock);
}

return count;
@@ -144,6 +148,8 @@ sock_err:
sockfd_put(socket);
err:
spin_unlock_irq(&sdev->ud.lock);
+unlock_mutex:
+ mutex_unlock(&sdev->ud.sysfs_lock);
return -EINVAL;
}
static DEVICE_ATTR(usbip_sockfd, S_IWUSR, NULL, store_sockfd);
@@ -309,6 +315,7 @@ static struct stub_device *stub_device_a
sdev->ud.side = USBIP_STUB;
sdev->ud.status = SDEV_ST_AVAILABLE;
spin_lock_init(&sdev->ud.lock);
+ mutex_init(&sdev->ud.sysfs_lock);
sdev->ud.tcp_socket = NULL;
sdev->ud.sockfd = -1;