git: bb9bee1ffbb2 - stable/12 - usb(4): Fix for use after free in combination with EVDEV_SUPPORT.

The branch stable/12 has been updated by hselasky:

URL: https://cgit.FreeBSD.org/src/commit/?id=bb9bee1ffbb27f903bfd2c11d681d331bea727ea

commit bb9bee1ffbb27f903bfd2c11d681d331bea727ea
Author:     Hans Petter Selasky <hselasky@FreeBSD.org>
AuthorDate: 2021-10-24 11:38:04 +0000
Commit:     Hans Petter Selasky <hselasky@FreeBSD.org>
CommitDate: 2021-11-02 08:43:44 +0000

    usb(4): Fix for use after free in combination with EVDEV_SUPPORT.
    
    When EVDEV_SUPPORT was introduced, the USB transfers may be running
    after the main FIFO is closed. In connection to this a race may appear
    which can lead to use-after-free scenarios. Fix this for all FIFO
    consumers by initializing and resetting the FIFO queues under the
    lock used by the client. Then the client driver will see an empty
    queue in all cases a race may appear.
    
    Found by:       pho@
    Sponsored by:   NVIDIA Networking
    
    (cherry picked from commit aad0c65d6b37364d8ba92ecb8c85e004398a5194)
---
 sys/dev/usb/usb_dev.c | 47 ++++++++++++++++++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 13 deletions(-)

diff --git a/sys/dev/usb/usb_dev.c b/sys/dev/usb/usb_dev.c
index 9cd54bf0032c..d1a65bf8561b 100644
--- a/sys/dev/usb/usb_dev.c
+++ b/sys/dev/usb/usb_dev.c
@@ -1951,18 +1951,30 @@ int
 usb_fifo_alloc_buffer(struct usb_fifo *f, usb_size_t bufsize,
     uint16_t nbuf)
 {
+	struct usb_ifqueue temp_q = {};
+	void *queue_data;
+
 	usb_fifo_free_buffer(f);
 
-	/* allocate an endpoint */
-	f->free_q.ifq_maxlen = nbuf;
-	f->used_q.ifq_maxlen = nbuf;
+	temp_q.ifq_maxlen = nbuf;
 
-	f->queue_data = usb_alloc_mbufs(
-	    M_USBDEV, &f->free_q, bufsize, nbuf);
+	queue_data = usb_alloc_mbufs(
+	    M_USBDEV, &temp_q, bufsize, nbuf);
 
-	if ((f->queue_data == NULL) && bufsize && nbuf) {
+	if (queue_data == NULL && bufsize != 0 && nbuf != 0)
 		return (ENOMEM);
-	}
+
+	mtx_lock(f->priv_mtx);
+
+	/*
+	 * Setup queues and sizes under lock to avoid early use by
+	 * concurrent FIFO access:
+	 */
+	f->free_q = temp_q;
+	f->used_q.ifq_maxlen = nbuf;
+	f->queue_data = queue_data;
+	mtx_unlock(f->priv_mtx);
+
 	return (0);			/* success */
 }
 
@@ -1975,15 +1987,24 @@ usb_fifo_alloc_buffer(struct usb_fifo *f, usb_size_t bufsize,
 void
 usb_fifo_free_buffer(struct usb_fifo *f)
 {
-	if (f->queue_data) {
-		/* free old buffer */
-		free(f->queue_data, M_USBDEV);
-		f->queue_data = NULL;
-	}
-	/* reset queues */
+	void *queue_data;
+
+	mtx_lock(f->priv_mtx);
+
+	/* Get and clear pointer to free, if any. */
+	queue_data = f->queue_data;
+	f->queue_data = NULL;
 
+	/*
+	 * Reset queues under lock to avoid use of freed buffers by
+	 * concurrent FIFO activity:
+	 */
 	memset(&f->free_q, 0, sizeof(f->free_q));
 	memset(&f->used_q, 0, sizeof(f->used_q));
+	mtx_unlock(f->priv_mtx);
+
+	/* Free old buffer, if any. */
+	free(queue_data, M_USBDEV);
 }
 
 void