ipv6: Fix memleak of nhc_pcpu_rth_output in fib_check_nh_v6_gw().

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ipv6: Fix memleak of nhc_pcpu_rth_output in fib_check_nh_v6_gw(). fib_check_nh_v6_gw() expects that fib6_nh_init() cleans up everything when it fails. Commit 7dd73168e273 ("ipv6: Always allocate pcpu memory in a fib6_nh") moved fib_nh_common_init() before alloc_percpu_gfp() within fib6_nh_init() but forgot to add cleanup for fib6_nh->nh_common.nhc_pcpu_rth_output in case it fails to allocate fib6_nh->rt6i_pcpu, resulting in memleak. Let's call fib_nh_common_release() and clear nhc_pcpu_rth_output in the error path. Note that we can remove the fib6_nh_release() call in nh_create_ipv6() later in net-next.git.

References

• https://git.kernel.org/stable/c/16267a5036173d0173377545b4b6021b081d0933
• https://git.kernel.org/stable/c/1bd12dfc058e1e68759d313d7727d68dbc1b8964
• https://git.kernel.org/stable/c/596a883c4ce2d2e9c175f25b98fed3a1f33fea38
• https://git.kernel.org/stable/c/77c41cdbe6bce476e08d3251c0d501feaf10a9f3
• https://git.kernel.org/stable/c/119dcafe36795a15ae53351cbbd6177aaf94ffef
• https://git.kernel.org/stable/c/29d91820184d5cbc70f3246d4911d96eaeb930d6
• https://git.kernel.org/stable/c/d3d5b4b5ae263c3225db363ba08b937e2e2b0380
• https://git.kernel.org/stable/c/9740890ee20e01f99ff1dde84c63dcf089fabb98