[Qemu-devel] [PATCH for-3.1 2/2] usb-mtp: outlaw slashes in filenames

[Gerd Hoffmann <kraxel@redhat.com>]

Slash is unix directory separator, so they are not allowed in filenames.
Note this also stops the classic escape via "../".

Fixes: CVE-2018-16867
Reported-by: Michael Hanselmann (hansmi.ch)
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 hw/usb/dev-mtp.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/usb/dev-mtp.c b/hw/usb/dev-mtp.c
index fbe1ace035..87eeac1084 100644
--- a/hw/usb/dev-mtp.c
+++ b/hw/usb/dev-mtp.c
@@ -1718,6 +1718,12 @@ static void usb_mtp_write_metadata(MTPState *s)
 
     filename = utf16_to_str(dataset->length, dataset->filename);
 
+    if (strchr(filename, '/')) {
+        usb_mtp_queue_result(s, RES_INVALID_PARAMETER, d->trans,
+                             0, 0, 0, 0);
+        return;
+    }
+
     o = usb_mtp_object_lookup_name(p, filename, dataset->length);
     if (o != NULL) {
         next_handle = o->handle;
-- 
2.9.3