In the Linux kernel, the following vulnerability has been resolved: ipv4: stop exception dump...

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

ipv4: stop exception dump when nexthop group shrinks

Commit 4ce5dc9316de ("inet: switch inet_dump_fib() to RCU protection") allowed IPv4 FIB dumps to run concurrently with nexthop replacement.

fib_dump_info_fnhe() uses fib_info_num_path() as the loop bound, then fib_info_nhc() independently reloads nh->nh_grp. If RTM_NEWNEXTHOP replaces a group with fewer paths between those loads, fib_info_nhc() returns NULL and the dump dereferences it through nhc_flags.

Stop the walk when the indexed path is absent. Nexthop groups are dense, so the current snapshot has no later path.