From: Leon Hwang <leon.hwang@linux.dev> maillist inclusion category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/9693 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=... -------------------------------- 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. Fixes: 448325199f57 ("bpf: Add copy_map_value_long to copy to remote percpu memory") Signed-off-by: Leon Hwang <leon.hwang@linux.dev> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20260624155115.85196-2-leon.hwang@linux.dev Conflicts: include/linux/bpf.h [ctx conflicts] Signed-off-by: Pu Lehui <pulehui@huawei.com> --- include/linux/bpf.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index c337836a6c89..cc2a0cc4b411 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -500,7 +500,7 @@ static inline void bpf_obj_memcpy(struct btf_record *rec, if (IS_ERR_OR_NULL(rec)) { if (long_memcpy) - bpf_long_memcpy(dst, src, round_up(size, 8)); + bpf_long_memcpy(dst, src, size); else memcpy(dst, src, size); return; @@ -523,7 +523,7 @@ static inline void copy_map_value(struct bpf_map *map, void *dst, void *src) static inline void copy_map_value_long(struct bpf_map *map, void *dst, void *src) { - bpf_obj_memcpy(map->record, dst, src, map->value_size, true); + bpf_obj_memcpy(map->record, dst, src, round_up(map->value_size, 8), true); } static inline void bpf_obj_memzero(struct btf_record *rec, void *dst, u32 size) -- 2.34.1