In the Linux kernel, the following vulnerability has been resolved:

9p/net: fix improper handling of bogus negative read/write replies

In p9_client_write() and p9_client_read_once(), if the server
incorrectly replies with success but a negative write/read count then we
would consider written (negative) <= rsize (positive) because both
variables were signed.

Make variables unsigned to avoid this problem.

The reproducer linked below now fails with the following error instead
of a null pointer deref:
9pnet: bogus RWRITE count (4294967295 > 3)

https://git.kernel.org/stable/c/374e4cd75617c8c2552f562f39dd989583f5c330

https://git.kernel.org/stable/c/468ff4a7c61fb811c596a7c44b6a5455e40fd12b

https://git.kernel.org/stable/c/a68768e280b7d0c967ea509e791bb9b90adc94a5

https://git.kernel.org/stable/c/c548f95688e2b5ae0e2ae43d53cf717156c7d034

https://git.kernel.org/stable/c/d0259a856afca31d699b706ed5e2adf11086c73b