ipv6: fix another slab-out-of-bounds in fib6_nh_flush_exceptions

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ipv6: fix another slab-out-of-bounds in fib6_nh_flush_exceptions While running the self-tests on a KASAN enabled kernel, I observed a slab-out-of-bounds splat very similar to the one reported in commit 821bbf79fe46 ("ipv6: Fix KASAN: slab-out-of-bounds Read in fib6_nh_flush_exceptions"). We additionally need to take care of fib6_metrics initialization failure when the caller provides an nh. The fix is similar, explicitly free the route instead of calling fib6_info_release on a half-initialized object.

References

• https://git.kernel.org/stable/c/830251361425c5be044db4d826aaf304ea3d14c6
• https://git.kernel.org/stable/c/ce8fafb68051fba52546f8bbe8621f7641683680
• https://git.kernel.org/stable/c/115784bcccf135c3a3548098153413d76f16aae0
• https://git.kernel.org/stable/c/8fb4792f091e608a0a1d353dfdf07ef55a719db5