diff mbox series

[PULL,5/5] usb-mtp: Limit filename to object information size

Message ID 20181214103854.13820-6-kraxel@redhat.com
State New
Headers show
Series [PULL,1/5] pvusb: set max grants only in initialise | expand

Commit Message

Gerd Hoffmann Dec. 14, 2018, 10:38 a.m. UTC 
From: Michael Hanselmann <public@hansmi.ch>

The filename length in MTP metadata is specified by the guest. By
trusting it directly it'd theoretically be possible to get the host to
write memory parts outside the filename buffer into a filename. In
practice though there are usually NUL bytes stopping the string
operations.

Also use the opportunity to not assign the filename member twice.

Signed-off-by: Michael Hanselmann <public@hansmi.ch>
Message-id: ab70659d8d5c580bdf150a5f7d5cc60c8e374ffc.1544740018.git.public@hansmi.ch

[ kraxel: codestyle fix: break a long line ]

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 hw/usb/dev-mtp.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/hw/usb/dev-mtp.c b/hw/usb/dev-mtp.c
index 36c43b8c20..6098005cd4 100644
--- a/hw/usb/dev-mtp.c
+++ b/hw/usb/dev-mtp.c
@@ -1710,7 +1710,7 @@  free:
     s->write_pending = false;
 }
 
-static void usb_mtp_write_metadata(MTPState *s)
+static void usb_mtp_write_metadata(MTPState *s, uint64_t dlen)
 {
     MTPData *d = s->data_out;
     ObjectInfo *dataset = (ObjectInfo *)d->data;
@@ -1722,7 +1722,9 @@  static void usb_mtp_write_metadata(MTPState *s)
     assert(!s->write_pending);
     assert(p != NULL);
 
-    filename = utf16_to_str(dataset->length, dataset->filename);
+    filename = utf16_to_str(MIN(dataset->length,
+                                dlen - offsetof(ObjectInfo, filename)),
+                            dataset->filename);
 
     if (strchr(filename, '/')) {
         usb_mtp_queue_result(s, RES_PARAMETER_NOT_SUPPORTED, d->trans,
@@ -1738,7 +1740,6 @@  static void usb_mtp_write_metadata(MTPState *s)
     s->dataset.filename = filename;
     s->dataset.format = dataset->format;
     s->dataset.size = dataset->size;
-    s->dataset.filename = filename;
     s->write_pending = true;
 
     if (s->dataset.format == FMT_ASSOCIATION) {
@@ -1807,7 +1808,7 @@  static void usb_mtp_get_data(MTPState *s, mtp_container *container,
         if (d->offset == d->length) {
             /* The operation might have already failed */
             if (!s->result) {
-                usb_mtp_write_metadata(s);
+                usb_mtp_write_metadata(s, dlen);
             }
             usb_mtp_data_free(s->data_out);
             s->data_out = NULL;