On Fri, May 20, 2022 at 04:57:53PM -0700, Song Liu wrote:
> Introduce bpf_arch_text_invalidate and use it to fill unused part of the
> bpf_prog_pack with illegal instructions when a BPF program is freed.
>
> Signed-off-by: Song Liu <song@xxxxxxxxxx>
> ---
> arch/x86/net/bpf_jit_comp.c | 5 +++++
> include/linux/bpf.h | 1 +
> kernel/bpf/core.c | 8 ++++++++
> 3 files changed, 14 insertions(+)
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index a2b6d197c226..f298b18a9a3d 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -228,6 +228,11 @@ static void jit_fill_hole(void *area, unsigned int size)
> memset(area, 0xcc, size);
> }
>
> +int bpf_arch_text_invalidate(void *dst, size_t len)
> +{
> + return IS_ERR_OR_NULL(text_poke_set(dst, 0xcc, len));
> +}
> +
> struct jit_context {
> int cleanup_addr; /* Epilogue code offset */
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index cc4d5e394031..a9b1875212f6 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -2365,6 +2365,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
> void *addr1, void *addr2);
>
> void *bpf_arch_text_copy(void *dst, void *src, size_t len);
> +int bpf_arch_text_invalidate(void *dst, size_t len);
>
> struct btf_id_set;
> bool btf_id_set_contains(const struct btf_id_set *set, u32 id);
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 2d0c9d4696ad..cacd8684c3c4 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -968,6 +968,9 @@ static void bpf_prog_pack_free(struct bpf_binary_header *hdr)
> nbits = BPF_PROG_SIZE_TO_NBITS(hdr->size);
> pos = ((unsigned long)hdr - (unsigned long)pack_ptr) >> BPF_PROG_CHUNK_SHIFT;
>
> + WARN_ONCE(bpf_arch_text_invalidate(hdr, hdr->size),
> + "bpf_prog_pack bug: missing bpf_arch_text_invalidate?\n");
Why is this a WARN?
What happens if bpf_arch_text_invalidate() is implemented but returns an error?
> +
> bitmap_clear(pack->bitmap, pos, nbits);
> if (bitmap_find_next_zero_area(pack->bitmap, bpf_prog_chunk_count(), 0,
> bpf_prog_chunk_count(), 0) == 0) {
> @@ -2740,6 +2743,11 @@ void * __weak bpf_arch_text_copy(void *dst, void *src, size_t len)
> return ERR_PTR(-ENOTSUPP);
> }
>
> +int __weak bpf_arch_text_invalidate(void *dst, size_t len)
> +{
> + return -ENOTSUPP;
> +}
> +
> DEFINE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
> EXPORT_SYMBOL(bpf_stats_enabled_key);
>
> --
> 2.30.2
>
>
--
Sincerely yours,
Mike.
