Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:  net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop  When a standalone IPv6 nexthop object is created with a loopback device (e.g., "ip -6 nexthop add id 100 dev lo"), fib6_nh_init() misclassifies it as a reject route. This is because nexthop objects have no destination prefix (fc_dst=::), causing fib6_is_reject() to match any loopback nexthop. The reject path skips fib_nh_common_init(), leaving nhc_pcpu_rth_output unallocated. If an IPv4 route later references this nexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and panics.  Simplify the check in fib6_nh_init() to only match explicit reject routes (RTF_REJECT) instead of using fib6_is_reject(). The loopback promotion heuristic in fib6_is_reject() is handled separately by ip6_route_info_create_nh(). After this change, the three cases behave as follows:  1. Explicit reject route ("ip -6 route add unreachable 2001:db8::/64"):    RTF_REJECT is set, enters reject path, skips fib_nh_common_init().    No behavior change.  2. Implicit loopback reject route ("ip -6 route add 2001:db8::/32 dev lo"):    RTF_REJECT is not set, takes normal path, fib_nh_common_init() is    called. ip6_route_info_create_nh() still promotes it to reject    afterward. nhc_pcpu_rth_output is allocated but unused, which is    harmless.  3. Standalone nexthop object ("ip -6 nexthop add id 100 dev lo"):    RTF_REJECT is not set, takes normal path, fib_nh_common_init() is    called. nhc_pcpu_rth_output is properly allocated, fixing the crash    when IPv4 routes reference this nexthop.