[PATCH 4.14 20/68] usbip: synchronize event handler with sysfs code paths

Greg Kroah-Hartman
2021-04-15T14:58:13Z

From: Shuah Khan <skhan@linuxfoundation.org>

commit 363eaa3a450abb4e63bd6e3ad79d1f7a0f717814 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 synchronize event handler with sysfs paths
in usbip drivers.

Cc: stable@vger.kernel.org
Reported-and-tested-by: syzbot+a93fba6d384346a761e3@syzkaller.appspotmail.com
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/c5c8723d3f29dfe3d759cfaafa7dd16b0dfe2918.1616807117.git.skhan@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/usbip/usbip_event.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/usb/usbip/usbip_event.c
+++ b/drivers/usb/usbip/usbip_event.c
@@ -84,6 +84,7 @@ static void event_handler(struct work_st
while ((ud = get_event()) != NULL) {
usbip_dbg_eh("pending event %lx\n", ud->event);

+ mutex_lock(&ud->sysfs_lock);
/*
* NOTE: shutdown must come first.
* Shutdown the device.
@@ -104,6 +105,7 @@ static void event_handler(struct work_st
ud->eh_ops.unusable(ud);
unset_event(ud, USBIP_EH_UNUSABLE);
}
+ mutex_unlock(&ud->sysfs_lock);

wake_up(&ud->eh_waitq);
}