This is a note to let you know that I've just added the patch titled cdc-acm: prevent infinite loop when parsing CDC headers. to the 4.0-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: cdc-acm-prevent-infinite-loop-when-parsing-cdc-headers.patch and it can be found in the queue-4.0 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 0d3bba0287d4e284c3ec7d3397e81eec920d5e7e Mon Sep 17 00:00:00 2001 From: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx> Date: Tue, 14 Apr 2015 11:25:43 +0200 Subject: cdc-acm: prevent infinite loop when parsing CDC headers. From: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx> 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@xxxxxxxxxx> Signed-off-by: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx> CC: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx> CC: Oliver Neukum <oneukum@xxxxxxx> CC: Adam Lee <adam8157@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 */ Patches currently in stable-queue which might be from quentin.casasnovas@xxxxxxxxxx are queue-4.0/cdc-acm-prevent-infinite-loop-when-parsing-cdc-headers.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html