libbpf: Verify that arena map exists when adding arena relocations

[ Upstream commit 42be23e8f2dcb100cb9944b2b54b6bf41aff943d ]

Fuzzer reported a memory access error in bpf_program__record_reloc()
that happens when:
- ".addr_space.1" section exists
- there is a relocation referencing this section
- there are no arena maps defined in BTF.

Sanity checks for maps existence are already present in
bpf_program__record_reloc(), hence this commit adds another one.

[1] https://github.com/libbpf/libbpf/actions/runs/16375110681/job/46272998064

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250718222059.281526-1-eddyz87@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index d41ee26b944359d2a8c307ee082b52d03b98bebf..6401dd3bd35fafcb74a6f4a9725da2343c2c95d9 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4582,6 +4582,11 @@ static int bpf_program__record_reloc(struct bpf_program *prog,
 
        /* arena data relocation */
        if (shdr_idx == obj->efile.arena_data_shndx) {
+               if (obj->arena_map_idx < 0) {
+                       pr_warn("prog '%s': bad arena data relocation at insn %u, no arena maps defined\n",
+                               prog->name, insn_idx);
+                       return -LIBBPF_ERRNO__RELOC;
+               }
                reloc_desc->type = RELO_DATA;
                reloc_desc->insn_idx = insn_idx;
                reloc_desc->map_idx = obj->arena_map_idx;