diff options
| author | Quentin Casasnovas <quentin.casasnovas@oracle.com> | 2015-04-14 11:25:43 +0200 |
|---|---|---|
| committer | Zefan Li <lizefan@huawei.com> | 2015-06-19 11:40:34 +0800 |
| commit | b383c48a15768f2013a38e20b2bba82d04b53dcf (patch) | |
| tree | d7165097023864b3f474e486779981584e600834 | |
| parent | 981889fbaee9c2851727f534deb425b85a15e641 (diff) | |
cdc-acm: prevent infinite loop when parsing CDC headers.
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>
Signed-off-by: Zefan Li <lizefan@huawei.com>
| -rw-r--r-- | drivers/usb/class/cdc-acm.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 57877a98db46..25bc1d6e7d58 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1044,11 +1044,16 @@ static int acm_probe(struct usb_interface *intf, } 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 */ |