| Message ID | 20190918120147.4520-1-bjorn@mork.no (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 3fe4b3351301660653a2bc73f2226da0ebd2b95e |
| Headers | show |
| Series | [net,stable] cdc_ncm: fix divide-by-zero caused by invalid wMaxPacketSize | expand |
Hello, syzbot has tested the proposed patch and the reproducer did not trigger crash: Reported-and-tested-by: syzbot+ce366e2b8296e25d84f5@syzkaller.appspotmail.com Tested on: commit: f0df5c1b usb-fuzzer: main usb gadget fuzzer driver git tree: https://github.com/google/kasan.git kernel config: https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5 dashboard link: https://syzkaller.appspot.com/bug?extid=ce366e2b8296e25d84f5 compiler: gcc (GCC) 9.0.0 20181231 (experimental) patch: https://syzkaller.appspot.com/x/patch.diff?x=114971b5600000 Note: testing is done by a robot and is best-effort only.
On Wed, 18 Sep 2019 14:01:46 +0200, Bjørn Mork wrote: > Endpoints with zero wMaxPacketSize are not usable for transferring > data. Ignore such endpoints when looking for valid in, out and > status pipes, to make the driver more robust against invalid and > meaningless descriptors. > > The wMaxPacketSize of the out pipe is used as divisor. So this change > fixes a divide-by-zero bug. > > Reported-by: syzbot+ce366e2b8296e25d84f5@syzkaller.appspotmail.com > Signed-off-by: Bjørn Mork <bjorn@mork.no> Applied, queued, thank you!
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c index 50c05d0f44cb..00cab3f43a4c 100644 --- a/drivers/net/usb/cdc_ncm.c +++ b/drivers/net/usb/cdc_ncm.c @@ -681,8 +681,12 @@ cdc_ncm_find_endpoints(struct usbnet *dev, struct usb_interface *intf) u8 ep; for (ep = 0; ep < intf->cur_altsetting->desc.bNumEndpoints; ep++) { - e = intf->cur_altsetting->endpoint + ep; + + /* ignore endpoints which cannot transfer data */ + if (!usb_endpoint_maxp(&e->desc)) + continue; + switch (e->desc.bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) { case USB_ENDPOINT_XFER_INT: if (usb_endpoint_dir_in(&e->desc)) {
Endpoints with zero wMaxPacketSize are not usable for transferring data. Ignore such endpoints when looking for valid in, out and status pipes, to make the driver more robust against invalid and meaningless descriptors. The wMaxPacketSize of the out pipe is used as divisor. So this change fixes a divide-by-zero bug. Reported-by: syzbot+ce366e2b8296e25d84f5@syzkaller.appspotmail.com Signed-off-by: Bjørn Mork <bjorn@mork.no> --- #syz test: https://github.com/google/kasan.git f0df5c1b drivers/net/usb/cdc_ncm.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)