> On Jan 15, 2019, at 2:54 PM, Stanislav Fomichev <s...@google.com> wrote:
>
> Build-id length is not fixed to 20, it can be (`man ld` /--build-id):
> * 128-bit (uuid)
> * 160-bit (sha1)
> * any length specified in ld --build-id=0xhexstring
>
> To fix the issue of missing BPF_STACK_BUILD_ID_VALID for shorter build-ids,
> assume that build-id is somewhere in the range of 1 .. 20.
> Set the remaining bytes to zero.
>
> Fixes: 615755a77b24 ("bpf: extend stackmap to save binary_build_id+offset
> instead of address")
> Signed-off-by: Stanislav Fomichev <s...@google.com>
> ---
> kernel/bpf/stackmap.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
> index d9e2483669d0..8975d1768dcb 100644
> --- a/kernel/bpf/stackmap.c
> +++ b/kernel/bpf/stackmap.c
> @@ -180,11 +180,15 @@ static inline int stack_map_parse_build_id(void
> *page_addr,
>
> if (nhdr->n_type == BPF_BUILD_ID &&
> nhdr->n_namesz == sizeof("GNU") &&
> - nhdr->n_descsz == BPF_BUILD_ID_SIZE) {
> + nhdr->n_descsz > 0 &&
> + nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
> + __u32 len = min_t(__u32,
> + BPF_BUILD_ID_SIZE, nhdr->n_descsz);
Given the check above, we only need len = nhdr->n_descsz, right?
Other than this,
Acked-by: Song Liu <songliubrav...@fb.com>
Thanks for the fix!
> memcpy(build_id,
> note_start + note_offs +
> ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
> - BPF_BUILD_ID_SIZE);
> + len);
> + memset(build_id + len, 0, BPF_BUILD_ID_SIZE - len);
> return 0;
> }
> new_offs = note_offs + sizeof(Elf32_Nhdr) +
> --
> 2.20.1.97.g81188d93c3-goog
>
