[PATCH 4.15 018/128] usb: usbmon: Read text within supplied buffer size

Greg Kroah-Hartman
2018-03-16T15:22:39Z

From: Pete Zaitcev <zaitcev@kotori.zaitcev.us>

commit a5f596830e27e15f7a0ecd6be55e433d776986d8 upstream.

This change fixes buffer overflows and silent data corruption with the
usbmon device driver text file read operations.

Signed-off-by: Fredrik Noring <noring@nocrew.org>
Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/mon/mon_text.c | 124 +++++++++++++++++++++++++++------------------
1 file changed, 77 insertions(+), 47 deletions(-)

--- a/drivers/usb/mon/mon_text.c
+++ b/drivers/usb/mon/mon_text.c
@@ -85,6 +85,8 @@ struct mon_reader_text {

wait_queue_head_t wait;
int printf_size;
+ size_t printf_offset;
+ size_t printf_togo;
char *printf_buf;
struct mutex printf_lock;

@@ -376,75 +378,103 @@ err_alloc:
return rc;
}

-/*
- * For simplicity, we read one record in one system call and throw out
- * what does not fit. This means that the following does not work:
- * dd if=/dbg/usbmon/0t bs=10
- * Also, we do not allow seeks and do not bother advancing the offset.
- */
+static ssize_t mon_text_copy_to_user(struct mon_reader_text *rp,
+ char __user * const buf, const size_t nbytes)
+{
+ const size_t togo = min(nbytes, rp->printf_togo);
+
+ if (copy_to_user(buf, &rp->printf_buf[rp->printf_offset], togo))
+ return -EFAULT;
+ rp->printf_togo -= togo;
+ rp->printf_offset += togo;
+ return togo;
+}
+
+/* ppos is not advanced since the llseek operation is not permitted. */
static ssize_t mon_text_read_t(struct file *file, char __user *buf,
- size_t nbytes, loff_t *ppos)
+ size_t nbytes, loff_t *ppos)
{
struct mon_reader_text *rp = file->private_data;
struct mon_event_text *ep;
struct mon_text_ptr ptr;
+ ssize_t ret;

- ep = mon_text_read_wait(rp, file);
- if (IS_ERR(ep))
- return PTR_ERR(ep);
mutex_lock(&rp->printf_lock);
- ptr.cnt = 0;
- ptr.pbuf = rp->printf_buf;
- ptr.limit = rp->printf_size;
-
- mon_text_read_head_t(rp, &ptr, ep);
- mon_text_read_statset(rp, &ptr, ep);
- ptr.cnt += snprintf(ptr.pbuf + ptr.cnt, ptr.limit - ptr.cnt,
- " %d", ep->length);
- mon_text_read_data(rp, &ptr, ep);

- if (copy_to_user(buf, rp->printf_buf, ptr.cnt))
- ptr.cnt = -EFAULT;
+ if (rp->printf_togo == 0) {
+
+ ep = mon_text_read_wait(rp, file);
+ if (IS_ERR(ep)) {
+ mutex_unlock(&rp->printf_lock);
+ return PTR_ERR(ep);
+ }
+ ptr.cnt = 0;
+ ptr.pbuf = rp->printf_buf;
+ ptr.limit = rp->printf_size;
+
+ mon_text_read_head_t(rp, &ptr, ep);
+ mon_text_read_statset(rp, &ptr, ep);
+ ptr.cnt += snprintf(ptr.pbuf + ptr.cnt, ptr.limit - ptr.cnt,
+ " %d", ep->length);
+ mon_text_read_data(rp, &ptr, ep);
+
+ rp->printf_togo = ptr.cnt;
+ rp->printf_offset = 0;
+
+ kmem_cache_free(rp->e_slab, ep);
+ }
+
+ ret = mon_text_copy_to_user(rp, buf, nbytes);
mutex_unlock(&rp->printf_lock);
- kmem_cache_free(rp->e_slab, ep);
- return ptr.cnt;
+ return ret;
}

+/* ppos is not advanced since the llseek operation is not permitted. */
static ssize_t mon_text_read_u(struct file *file, char __user *buf,
- size_t nbytes, loff_t *ppos)
+ size_t nbytes, loff_t *ppos)
{
struct mon_reader_text *rp = file->private_data;
struct mon_event_text *ep;
struct mon_text_ptr ptr;
+ ssize_t ret;

- ep = mon_text_read_wait(rp, file);
- if (IS_ERR(ep))
- return PTR_ERR(ep);
mutex_lock(&rp->printf_lock);
- ptr.cnt = 0;
- ptr.pbuf = rp->printf_buf;
- ptr.limit = rp->printf_size;

- mon_text_read_head_u(rp, &ptr, ep);
- if (ep->type == 'E') {
- mon_text_read_statset(rp, &ptr, ep);
- } else if (ep->xfertype == USB_ENDPOINT_XFER_ISOC) {
- mon_text_read_isostat(rp, &ptr, ep);
- mon_text_read_isodesc(rp, &ptr, ep);
- } else if (ep->xfertype == USB_ENDPOINT_XFER_INT) {
- mon_text_read_intstat(rp, &ptr, ep);
- } else {
- mon_text_read_statset(rp, &ptr, ep);
+ if (rp->printf_togo == 0) {
+
+ ep = mon_text_read_wait(rp, file);
+ if (IS_ERR(ep)) {
+ mutex_unlock(&rp->printf_lock);
+ return PTR_ERR(ep);
+ }
+ ptr.cnt = 0;
+ ptr.pbuf = rp->printf_buf;
+ ptr.limit = rp->printf_size;
+
+ mon_text_read_head_u(rp, &ptr, ep);
+ if (ep->type == 'E') {
+ mon_text_read_statset(rp, &ptr, ep);
+ } else if (ep->xfertype == USB_ENDPOINT_XFER_ISOC) {
+ mon_text_read_isostat(rp, &ptr, ep);
+ mon_text_read_isodesc(rp, &ptr, ep);
+ } else if (ep->xfertype == USB_ENDPOINT_XFER_INT) {
+ mon_text_read_intstat(rp, &ptr, ep);
+ } else {
+ mon_text_read_statset(rp, &ptr, ep);
+ }
+ ptr.cnt += snprintf(ptr.pbuf + ptr.cnt, ptr.limit - ptr.cnt,
+ " %d", ep->length);
+ mon_text_read_data(rp, &ptr, ep);
+
+ rp->printf_togo = ptr.cnt;
+ rp->printf_offset = 0;
+
+ kmem_cache_free(rp->e_slab, ep);
}
- ptr.cnt += snprintf(ptr.pbuf + ptr.cnt, ptr.limit - ptr.cnt,
- " %d", ep->length);
- mon_text_read_data(rp, &ptr, ep);

- if (copy_to_user(buf, rp->printf_buf, ptr.cnt))
- ptr.cnt = -EFAULT;
+ ret = mon_text_copy_to_user(rp, buf, nbytes);
mutex_unlock(&rp->printf_lock);
- kmem_cache_free(rp->e_slab, ep);
- return ptr.cnt;
+ return ret;
}

static struct mon_event_text *mon_text_read_wait(struct mon_reader_text *rp,