btf: fix bug with resolving STRUCT/UNION into corresponding FWD

When checking available canonical candidates for struct/union algorithm
utilizes btf_dedup_is_equiv to determine if candidate is suitable. This
check is not enough when candidate is corresponding FWD for that
struct/union, because according to equivalence logic they are
equivalent. When it so happens that FWD and STRUCT/UNION end in hashing
to the same bucket, it's possible to create remapping loop from FWD to
STRUCT and STRUCT to same FWD, which will cause btf_dedup() to loop
forever.

This patch fixes the issue by additionally checking that type and
canonical candidate are strictly equal (utilizing btf_equal_struct).

Fixes: d5caef5b5655 ("btf: add BTF types deduplication algorithm")
Reported-by: Arnaldo Carvalho de Melo <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Acked-by: Song Liu <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>

0 files changed, 0 insertions, 0 deletions