CVE-2026-93174bpf: Copy per-CPU map value padding in copy_map_value_long()

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/e0653c8f718109d140e806daac166c43e2b2b8bd
• https://git.kernel.org/stable/c/953e85da53541a8dc3e7ad4e8532f29a34a32eae
• https://git.kernel.org/stable/c/003bf840ed3326bd01396ce7d5b431cef0d371e7
• https://git.kernel.org/stable/c/5e9f69829835521aa2942d1d14bd0990fbc6991e
• https://git.kernel.org/stable/c/ff3f22ed8d2f350b4c24ee26e33daea5f08d58ef
• https://git.kernel.org/stable/c/7cf9cd98cf6f0df3befc167ca6b54c07014d71de