udp: fix race between close() and udp_abort()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: udp: fix race between close() and udp_abort() Kaustubh reported and diagnosed a panic in udp_lib_lookup(). The root cause is udp_abort() racing with close(). Both racing functions acquire the socket lock, but udp{v6}_destroy_sock() release it before performing destructive actions. We can't easily extend the socket lock scope to avoid the race, instead use the SOCK_DEAD flag to prevent udp_abort from doing any action when the critical race happens. Diagnosed-and-tested-by: Kaustubh Pandey <kapandey@codeaurora.org>

References

• https://git.kernel.org/stable/c/e3c36c773aed0fef8b1d3d555b43393ec564400f
• https://git.kernel.org/stable/c/a0882f68f54f7a8b6308261acee9bd4faab5a69e
• https://git.kernel.org/stable/c/2f73448041bd0682d4b552cfd314ace66107f1ad
• https://git.kernel.org/stable/c/5a88477c1c85e4baa51e91f2d40f2166235daa56
• https://git.kernel.org/stable/c/8729ec8a2238152a4afc212a331a6cd2c61aeeac
• https://git.kernel.org/stable/c/65310b0aff86980a011c7c7bfa487a333d4ca241
• https://git.kernel.org/stable/c/a8b897c7bcd47f4147d066e22cc01d1026d7640e