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cdc-acm: prevent infinite loop when parsing CDC headers.
[ Upstream commit 0d3bba0287d4e284c3ec7d3397e81eec920d5e7e ] 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") Change-Id: Ie7ffa235e5200c8e376ecd80c75707dbad695930 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> CC: <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
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@ -1044,11 +1044,16 @@ static int acm_probe(struct usb_interface *intf,
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}
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while (buflen > 0) {
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elength = buffer[0];
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if (!elength) {
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dev_err(&intf->dev, "skipping garbage byte\n");
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elength = 1;
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goto next_desc;
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}
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if (buffer[1] != USB_DT_CS_INTERFACE) {
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dev_err(&intf->dev, "skipping garbage\n");
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goto next_desc;
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}
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elength = buffer[0];
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switch (buffer[2]) {
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case USB_CDC_UNION_TYPE: /* we've found it */
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