| From 0d3bba0287d4e284c3ec7d3397e81eec920d5e7e Mon Sep 17 00:00:00 2001 |
| From: Quentin Casasnovas <quentin.casasnovas@oracle.com> |
| Date: Tue, 14 Apr 2015 11:25:43 +0200 |
| Subject: cdc-acm: prevent infinite loop when parsing CDC headers. |
| |
| From: Quentin Casasnovas <quentin.casasnovas@oracle.com> |
| |
| commit 0d3bba0287d4e284c3ec7d3397e81eec920d5e7e upstream. |
| |
| Phil and I found out a problem with commit: |
| |
| 7e860a6e7aa6 ("cdc-acm: add sanity checks") |
| |
| It added some sanity checks to ignore potential garbage in CDC headers but |
| also introduced a potential infinite loop. This can happen at the first |
| loop iteration (elength = 0 in that case) if the description isn't a |
| DT_CS_INTERFACE or later if 'buffer[0]' is zero. |
| |
| It should also be noted that the wrong length was being added to 'buffer' |
| in case 'buffer[1]' was not a DT_CS_INTERFACE descriptor, since elength was |
| assigned after that check in the loop. |
| |
| A specially crafted USB device could be used to trigger this infinite loop. |
| |
| Fixes: 7e860a6e7aa6 ("cdc-acm: add sanity checks") |
| Signed-off-by: Phil Turnbull <phil.turnbull@oracle.com> |
| Signed-off-by: Quentin Casasnovas <quentin.casasnovas@oracle.com> |
| CC: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> |
| CC: Oliver Neukum <oneukum@suse.de> |
| CC: Adam Lee <adam8157@gmail.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/usb/class/cdc-acm.c | 7 ++++++- |
| 1 file changed, 6 insertions(+), 1 deletion(-) |
| |
| --- a/drivers/usb/class/cdc-acm.c |
| +++ b/drivers/usb/class/cdc-acm.c |
| @@ -1133,11 +1133,16 @@ static int acm_probe(struct usb_interfac |
| } |
| |
| while (buflen > 0) { |
| + elength = buffer[0]; |
| + if (!elength) { |
| + dev_err(&intf->dev, "skipping garbage byte\n"); |
| + elength = 1; |
| + goto next_desc; |
| + } |
| if (buffer[1] != USB_DT_CS_INTERFACE) { |
| dev_err(&intf->dev, "skipping garbage\n"); |
| goto next_desc; |
| } |
| - elength = buffer[0]; |
| |
| switch (buffer[2]) { |
| case USB_CDC_UNION_TYPE: /* we've found it */ |
