diff options
| author | Leon Hwang <leon.hwang@linux.dev> | 2026-06-24 23:51:14 +0800 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2026-07-01 11:27:37 -0700 |
| commit | 7cf9cd98cf6f0df3befc167ca6b54c07014d71de (patch) | |
| tree | ba9f785e6eebb69e564a0c77bab006114e693fe0 | |
| parent | f29997a6d920cdfa2c43995e17c596c599ff261b (diff) | |
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.
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
| -rw-r--r-- | include/linux/bpf.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 7719f6528445..ba09795e0bfd 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -570,7 +570,7 @@ 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; @@ -593,7 +593,7 @@ 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_swap_uptrs(const struct btf_record *rec, void *dst, void *src) |