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libbpf: fix off-by-one in emit_signature_match jump offset

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The offset for the cleanup-label jump is computed before the MOV R7
instruction is emitted, but the JMP lands after it. Account for the
extra insn in the offset calculation (-2 instead of -1). Drop the
redundant self-loop in the else branch; gen->error = -ERANGE already
marks the generation as failed.

Fixes: fb2b0e290147 ("libbpf: Update light skeleton for signing")
Signed-off-by: KP Singh <kpsingh@kernel.org>
Link: https://lore.kernel.org/r/20260522215337.662271-2-kpsingh@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
KP Singh authored and Andrii Nakryiko committed 2026-05-30 20:45:51 -07:00
1 parent 485dd4bb6c
commit 5a5b5b0dff
1 file changed
+1 -2
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src/gen_loader.c
+1 -2
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@@ -592,13 +592,12 @@ static void emit_signature_match(struct bpf_gen *gen)
gen->hash_insn_offset[i] = gen->insn_cur - gen->insn_start;
emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_3, 0, 0, 0, 0, 0));
off = -(gen->insn_cur - gen->insn_start - gen->cleanup_label) / 8 - 1;
off = -(gen->insn_cur - gen->insn_start - gen->cleanup_label) / 8 - 2;
if (is_simm16(off)) {
emit(gen, BPF_MOV64_IMM(BPF_REG_7, -EINVAL));
emit(gen, BPF_JMP_REG(BPF_JNE, BPF_REG_2, BPF_REG_3, off));
} else {
gen->error = -ERANGE;
emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, -1));
}
}
}