CVE-2021-47243 Information

Description

In the Linux kernel the following vulnerability has been resolved:

sch_cake: Fix out of bounds when parsing TCP options and header

The TCP option parser in cake qdisc (cake_get_tcpopt and cake_tcph_may_drop) could read one byte out of bounds. When the length is 1 the execution flow gets into the loop reads one byte of the opcode and if the opcode is neither TCPOPT_EOL nor TCPOPT_NOP it reads one more byte which exceeds the length of 1.

This fix is inspired by commit 9609dad263f8 (\ipv4: tcp_input: fix stack out of bounds when parsing TCP options.).

v2 changes:

Added doff validation in cake_get_tcphdr to avoid parsing garbage as TCP header. Although it wasn’t strictly an out-of-bounds access (memory was allocated) garbage values could be read where CAKE expected the TCP header if doff was smaller than 5.

Reference

https://git.kernel.org/stable/c/595897ef118d6fe66690c4fc5b572028c9da95b7 https://git.kernel.org/stable/c/4cefa061fc63f4d2dff5ab4083f43857cd7a2335 https://git.kernel.org/stable/c/3b491dd593d582ceeb27aa617600712a6bd14246 https://git.kernel.org/stable/c/3371392c60e2685af30bd4547badd880f5df2b3f https://git.kernel.org/stable/c/ba91c49dedbde758ba0b72f57ac90b06ddf8e548