CVE-2026-98025net: usb: cx82310_eth: drop URB after 0xffff reboot sentinel to prevent partial_data heap overflow

Official description

In the Linux kernel, the following vulnerability has been resolved: net: usb: cx82310_eth: drop URB after 0xffff reboot sentinel to prevent partial_data heap overflow The 0xffff length sentinel detects a router reboot and schedules re-enabling of ethernet mode, but then falls through to the rest of the loop body. The next check is } else if (len > CX82310_MTU) { which is the else of the just-matched if -- it never fires for len == 0xffff. The MTU bound that normally caps the incomplete-packet save path is silently bypassed. With 0xffff > skb->len always true (rx_urb_size is 4096), the incomplete-packet branch saves dev->partial_len = skb->len bytes into dev->partial_data. partial_data is kmalloc(hard_mtu) = kmalloc(CX82310_MTU + 2) = 1516 bytes, but skb->len after the 2-byte header pull can be up to 4094. A device that sends a 4096-byte URB starting with [0xff 0xff] therefore copies 4094 device-provided bytes into a buffer allocated for 1516 bytes, exceeding its requested size by 2578 bytes. The next URB then reads dev->partial_len (4094) back from the same 1516-byte buffer and dev->partial_rem (65535 - 4094 = 61441) from the new URB's ~4KB skb, both well past their allocations, and delivers the spliced result as a 64KB "frame" to the network stack. Bail out of rx_fixup after scheduling the re-enable work; the remainder of a reboot-marker URB is not meaningful packet data. This restores the invariant that partial_len < CX82310_MTU + 2 on the save path, since every other route there has already passed the MTU check.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/d0c1ce6ef4cefe568e19afa83f543caa3c3c0873
• https://git.kernel.org/stable/c/0dbc89e664b4609ad672b5bdeef60df251294b8f
• https://git.kernel.org/stable/c/00520cdd21ea6a9b5dc8d53bbd241620d2059554
• https://git.kernel.org/stable/c/59bf9e94bdc49557f07d87164269daff7340f4d6
• https://git.kernel.org/stable/c/3bd689409bb1c93bdc6dd8ec6cbf5161bc4f0287
• https://git.kernel.org/stable/c/659654654eb140851467af41d610473c100c7975
• https://git.kernel.org/stable/c/237c9ae7145772af147e4665f158938350fa5658
• https://git.kernel.org/stable/c/5d50e90add8b4a978395e893e81954d19d58a7c5