6.1-stable review patch. If anyone has any objections, please let me know.
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From: Alan Maguire alan.maguire@oracle.com
[ Upstream commit 8e64c387c942229c551d0f23de4d9993d3a2acb6 ]
Recently as a side-effect of
commit ac053946f5c4 ("compiler.h: introduce TYPEOF_UNQUAL() macro")
issues were observed in deduplication between modules and kernel BTF such that a large number of kernel types were not deduplicated so were found in module BTF (task_struct, bpf_prog etc). The root cause appeared to be a failure to dedup struct types, specifically those with members that were pointers with __percpu annotations.
The issue in dedup is at the point that we are deduplicating structures, we have not yet deduplicated reference types like pointers. If multiple copies of a pointer point at the same (deduplicated) integer as in this case, we do not see them as identical. Special handling already exists to deal with structures and arrays, so add pointer handling here too.
Reported-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Alan Maguire alan.maguire@oracle.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20250429161042.2069678-1-alan.maguire@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/btf.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 8224a797c2da5..f7e3209d6c641 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -3939,6 +3939,19 @@ static bool btf_dedup_identical_structs(struct btf_dedup *d, __u32 id1, __u32 id return true; }
+static bool btf_dedup_identical_ptrs(struct btf_dedup *d, __u32 id1, __u32 id2) +{ + struct btf_type *t1, *t2; + + t1 = btf_type_by_id(d->btf, id1); + t2 = btf_type_by_id(d->btf, id2); + + if (!btf_is_ptr(t1) || !btf_is_ptr(t2)) + return false; + + return t1->type == t2->type; +} + /* * Check equivalence of BTF type graph formed by candidate struct/union (we'll * call it "candidate graph" in this description for brevity) to a type graph @@ -4071,6 +4084,9 @@ static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id, */ if (btf_dedup_identical_structs(d, hypot_type_id, cand_id)) return 1; + /* A similar case is again observed for PTRs. */ + if (btf_dedup_identical_ptrs(d, hypot_type_id, cand_id)) + return 1; return 0; }