Consider the following program: r1 = map_value; /* low 32 bits are zero at runtime */ r6 = 0xdead000000000000; if w1 != 0 goto l1; l0: r1 += r6; r2 = *(u64 *)(r1 + 0); exit; l1: r6 = 0; goto l0; At the moment is_branch_taken() reports the jump as always taken, because it does not distinguish between BPF_JMP and BPF_JMP32 comparisons when processing 'if w1 != 0 ...'.
Unified · Split
| @@ -16337,6 +16337,13 @@ static int is_branch_taken(struct bpf_verifier_env *env, struct bpf_reg_state *r · 16336 unmodified lines | ||
| 16337 | 16337 | if (__is_pointer_value(false, reg1) || __is_pointer_value(false, reg2)) { |
| 16338 | 16338 | u64 val; |
| 16339 | 16339 | |
| 16340 | + /* | |
| 16341 | + * The low 32 bits of a valid pointer may well be zero, hence | |
| 16342 | + * nothing below applies to a 32-bit comparison. | |
| 16343 | + */ | |
| 16344 | + if (is_jmp32) | |
| 16345 | + return -1; | |
| 16346 | + | |
| 16340 | 16347 | /* arrange that reg2 is a scalar, and reg1 is a pointer */ |
| 16341 | 16348 | if (!is_reg_const(reg2, is_jmp32)) { |
| 16342 | 16349 | opcode = flip_opcode(opcode); |