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authorQuentin Casasnovas <quentin.casasnovas@oracle.com>2015-04-14 11:25:43 +0200
committerZefan Li <lizefan@huawei.com>2015-06-19 11:40:34 +0800
commitb383c48a15768f2013a38e20b2bba82d04b53dcf (patch)
parent981889fbaee9c2851727f534deb425b85a15e641 (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>
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 */