CVE-2026-93174

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

bpf: Copy per-CPU map value padding in copy_map_value_long()

In kernel, per-CPU map elements are stored with

round_up(map->value_size, 8) bytes. On UAPI lookup paths, it copies the

rounded size for each CPU into a temporary buffer.

However, copy_map_value_long() passes 'map->value_size' to

bpf_obj_memcpy(). When the map has special fields, bpf_obj_memcpy() copies

around those fields with memcpy(), and does not copy the tail padding

between 'map->value_size' and round_up(map->value_size, 8).

The temporary UAPI lookup buffers are allocated without __GFP_ZERO. As a

result, when the per-CPU map's value size is not equal to

round_up(map->value_size, 8), UAPI LOOKUP_ELEM and its variants can return

stale heap contents from that padding to user space. The same issue

applies to bpf_iter for per-CPU maps.

Pass round_up(map->value_size, 8) to bpf_obj_memcpy() from

copy_map_value_long(), so per-CPU maps both with and without special

fields copy the entire per-CPU slot. Remove the now redundant round_up()

from bpf_obj_memcpy()'s long_memcpy path.