Originally, it was possible for the DPE length check to overflow if
wDatagramIndex + wDatagramLength > U16_MAX. This could lead to an OoB
read.
Move the wDatagramIndex term to the other side of the inequality.
An existing condition ensures that wDatagramIndex < urb->actual_length.
Fixes: a2d274c62e44 ("usbnet: ipheth: add CDC NCM support")
Signed-off-by: Foster Snowhill <forst@xxxxxx>
---
v3:
Split out from a monolithic patch in v2 as an atomic change.
v2: https://lore.kernel.org/netdev/20240912211817.1707844-1-forst@xxxxxx/
No code changes. Update commit message to further clarify that
`ipheth` is not and does not aim to be a complete or spec-compliant
CDC NCM implementation.
v1: https://lore.kernel.org/netdev/20240907230108.978355-1-forst@xxxxxx/
---
drivers/net/usb/ipheth.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/usb/ipheth.c b/drivers/net/usb/ipheth.c
index 2084b940b4ea..4b590a5269fd 100644
--- a/drivers/net/usb/ipheth.c
+++ b/drivers/net/usb/ipheth.c
@@ -254,8 +254,8 @@ static int ipheth_rcvbulk_callback_ncm(struct urb *urb)
while (le16_to_cpu(dpe->wDatagramIndex) != 0 &&
le16_to_cpu(dpe->wDatagramLength) != 0) {
if (le16_to_cpu(dpe->wDatagramIndex) >= urb->actual_length ||
- le16_to_cpu(dpe->wDatagramIndex) +
- le16_to_cpu(dpe->wDatagramLength) > urb->actual_length) {
+ le16_to_cpu(dpe->wDatagramLength) > urb->actual_length -
+ le16_to_cpu(dpe->wDatagramIndex)) {
dev->net->stats.rx_length_errors++;
return retval;
}
--
2.45.1
