CVE-2023-53426

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

xsk: Fix xsk_diag use-after-free error during socket cleanup

Fix a use-after-free error that is possible if the xsk_diag interface is used after the socket has been unbound from the device. This can happen either due to the socket being closed or the device disappearing. In the early days of AF_XDP, the way we tested that a socket was not bound to a device was to simply check if the netdevice pointer in the xsk socket structure was NULL. Later, a better system was introduced by having an explicit state variable in the xsk socket struct. For example, the state of a socket that is on the way to being closed and has been unbound from the device is XSK_UNBOUND.

The commit in the Fixes tag below deleted the old way of signalling that a socket is unbound, setting dev to NULL. This in the belief that all code using the old way had been exterminated. That was unfortunately not true as the xsk diagnostics code was still using the old way and thus does not work as intended when a socket is going down. Fix this by introducing a test against the state variable. If the socket is in the state XSK_UNBOUND, simply abort the diagnostics netlink operation.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/3e019d8a05a38abb5c85d4f1e85fda964610aa14
• https://git.kernel.org/stable/c/595931912357fa3507e522a7f8a0a76e423c23e4
• https://git.kernel.org/stable/c/5979985f2d6b565b6cf0f79a62670a2855c0e96c
• https://git.kernel.org/stable/c/6436973164ea5506a495f39e56be5aea375e7832