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bpf: Fix verifier crash on BPF_NEG with pointer register #6080

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bpf: Fix verifier crash on BPF_NEG with pointer register #6080

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0252523
bpf: Skip scalar adjustment for BPF_NEG if dst is a pointer
listout Oct 1, 2025
323da5e
selftests/bpf: Add test for BPF_NEG alu on CONST_PTR_TO_MAP
mannkafai Oct 1, 2025
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3 changes: 2 additions & 1 deletion kernel/bpf/verifier.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15645,7 +15645,8 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
}

/* check dest operand */
if (opcode == BPF_NEG) {
if (opcode == BPF_NEG &&
regs[insn->dst_reg].type == SCALAR_VALUE) {
err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
err = err ?: adjust_scalar_min_max_vals(env, insn,
&regs[insn->dst_reg],
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18 changes: 18 additions & 0 deletions tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,24 @@ l0_%=: exit; \
: __clobber_all);
}

SEC("socket")
__description("map_ptr illegal alu op, map_ptr = -map_ptr")
__failure __msg("R0 invalid mem access 'scalar'")
__failure_unpriv __msg_unpriv("R0 pointer arithmetic prohibited")
__flag(BPF_F_ANY_ALIGNMENT)
__naked void map_ptr_illegal_alu_op(void)
{
asm volatile (" \
r0 = %[map_hash_48b] ll; \
r0 = -r0; \
r1 = 22; \
*(u64*)(r0 + 0) = r1; \
exit; \
" :
: __imm_addr(map_hash_48b)
: __clobber_all);
}

SEC("flow_dissector")
__description("flow_keys illegal alu op with variable offset")
__failure __msg("R7 pointer arithmetic on flow_keys prohibited")
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