Re: [PATCH v2 bpf-next 10/17] libbpf: tighten BTF type ID rewriting with error checking
From: Yonghong Song <hidden>
Date: 2021-04-22 16:50:45
Also in:
bpf
On 4/16/21 1:23 PM, Andrii Nakryiko wrote:
It should never fail, but if it does, it's better to know about this rather than end up with nonsensical type IDs.
So this is defensive programming. Maybe do another round of audit of the callers and if you didn't find any issue, you do not need to check not-happening condition here?
quoted hunk ↗ jump to hunk
Signed-off-by: Andrii Nakryiko <andrii@kernel.org> --- tools/lib/bpf/linker.c | 9 +++++++++ 1 file changed, 9 insertions(+)diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c index 283249df9831..d5dc1d401f57 100644 --- a/tools/lib/bpf/linker.c +++ b/tools/lib/bpf/linker.c@@ -1423,6 +1423,15 @@ static int linker_fixup_btf(struct src_obj *obj) static int remap_type_id(__u32 *type_id, void *ctx) { int *id_map = ctx; + int new_id = id_map[*type_id]; + + if (*type_id == 0) + return 0; + + if (new_id == 0) { + pr_warn("failed to find new ID mapping for original BTF type ID %u\n", *type_id); + return -EINVAL; + } *type_id = id_map[*type_id];