> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 5936f8e2996f..c5863487ee73 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -3935,9 +3935,16 @@ static inline int bpf_map_check_op_flags(struct
> bpf_map *map, u64 flags, u64 all
> if ((u32)flags & ~allowed_flags)
> return -EINVAL;
>
> + /* BPF_NOEXIST and BPF_EXIST are mutually exclusive. */
> + if ((flags & (BPF_NOEXIST | BPF_EXIST)) == (BPF_NOEXIST | BPF_EXIST))
> + return -EINVAL;
> +
> if ((flags & BPF_F_LOCK) && !btf_record_has_field(map->record,
> BPF_SPIN_LOCK))
> return -EINVAL;
>
> + if ((flags & BPF_F_LOCK) && btf_record_has_field(map->record,
> ~BPF_SPIN_LOCK))
> + return -EOPNOTSUPP;
> +
> if (!(flags & BPF_F_CPU) && flags >> 32)
> return -EINVAL;
[ ... ]
> diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
> index e2fe6c32822b..80b50091cbbf 100644
> --- a/kernel/bpf/bpf_local_storage.c
> +++ b/kernel/bpf/bpf_local_storage.c
> @@ -493,13 +493,6 @@ bpf_local_storage_update(void *owner, struct
> bpf_local_storage_map *smap,
> unsigned long flags;
> int err;
>
> - /* BPF_EXIST and BPF_NOEXIST cannot be both set */
> - if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
> - /* BPF_F_LOCK can only be used in a value with spin_lock */
> - unlikely((map_flags & BPF_F_LOCK) &&
> - !btf_record_has_field(smap->map.record, BPF_SPIN_LOCK)))
> - return ERR_PTR(-EINVAL);
^^^^
This validation was removed from bpf_local_storage_update() but it appears
that no call to bpf_map_check_op_flags() was added in the local storage map
update functions. For array and hash maps, calls to bpf_map_check_op_flags()
were added in array_map_update_elem() and htab_map_update_elem(). However,
the local storage update functions like bpf_cgrp_storage_update_elem(),
bpf_fd_inode_storage_update_elem(), and bpf_fd_sk_storage_update_elem() pass
map_flags directly to bpf_local_storage_update() without calling
bpf_map_check_op_flags() first.
The syscall path does call bpf_map_check_op_flags() in map_update_elem() with
allowed_flags set to ~0, which catches the NOEXIST/EXIST mutual exclusion and
BPF_F_LOCK validation. But with allowed_flags=~0, the check for unknown flags
((u32)flags & ~allowed_flags) always passes zero, meaning unknown flags like
8 or 16 would not be rejected.
The old check (map_flags & ~BPF_F_LOCK) > BPF_EXIST rejected any unknown flag
bits. Is there a missing call to bpf_map_check_op_flags() in the local storage
update functions that should specify the allowed flags?
> -
> if (gfp_flags == GFP_KERNEL && (map_flags & ~BPF_F_LOCK) != BPF_NOEXIST)
> return ERR_PTR(-EINVAL);
[ ... ]
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/21254704407
