Commit 0b698005 authored Jan 16, 2019 by Stanislav Fomichev Committed by Daniel Borkmann Jan 17, 2019

bpf: don't assume build-id length is always 20 bytes



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.

v2:
* don't introduce new "len = min(BPF_BUILD_ID_SIZE, nhdr->n_descsz)",
  we already know that nhdr->n_descsz <= BPF_BUILD_ID_SIZE if we enter
  this 'if' condition

Fixes: 615755a7 ("bpf: extend stackmap to save binary_build_id+offset instead of address")
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent 6e8ccb4f

kernel/bpf/stackmap.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -180,11 +180,14 @@ 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) {
		memcpy(build_id,
		note_start + note_offs +
		ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
		BPF_BUILD_ID_SIZE);
		nhdr->n_descsz);
		memset(build_id + nhdr->n_descsz, 0,
		BPF_BUILD_ID_SIZE - nhdr->n_descsz);
		return 0;
		}
		new_offs = note_offs + sizeof(Elf32_Nhdr) +

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