diff options
Diffstat (limited to 'kernel/bpf/verifier.c')
| -rw-r--r-- | kernel/bpf/verifier.c | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8a097a85d01b..6f5a9f51cc03 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5829,6 +5829,67 @@ static void scalar_min_max_or(struct bpf_reg_state *dst_reg, __update_reg_bounds(dst_reg); } +static void scalar32_min_max_xor(struct bpf_reg_state *dst_reg, + struct bpf_reg_state *src_reg) +{ + bool src_known = tnum_subreg_is_const(src_reg->var_off); + bool dst_known = tnum_subreg_is_const(dst_reg->var_off); + struct tnum var32_off = tnum_subreg(dst_reg->var_off); + s32 smin_val = src_reg->s32_min_value; + + /* Assuming scalar64_min_max_xor will be called so it is safe + * to skip updating register for known case. + */ + if (src_known && dst_known) + return; + + /* We get both minimum and maximum from the var32_off. */ + dst_reg->u32_min_value = var32_off.value; + dst_reg->u32_max_value = var32_off.value | var32_off.mask; + + if (dst_reg->s32_min_value >= 0 && smin_val >= 0) { + /* XORing two positive sign numbers gives a positive, + * so safe to cast u32 result into s32. + */ + dst_reg->s32_min_value = dst_reg->u32_min_value; + dst_reg->s32_max_value = dst_reg->u32_max_value; + } else { + dst_reg->s32_min_value = S32_MIN; + dst_reg->s32_max_value = S32_MAX; + } +} + +static void scalar_min_max_xor(struct bpf_reg_state *dst_reg, + struct bpf_reg_state *src_reg) +{ + bool src_known = tnum_is_const(src_reg->var_off); + bool dst_known = tnum_is_const(dst_reg->var_off); + s64 smin_val = src_reg->smin_value; + + if (src_known && dst_known) { + /* dst_reg->var_off.value has been updated earlier */ + __mark_reg_known(dst_reg, dst_reg->var_off.value); + return; + } + + /* We get both minimum and maximum from the var_off. */ + dst_reg->umin_value = dst_reg->var_off.value; + dst_reg->umax_value = dst_reg->var_off.value | dst_reg->var_off.mask; + + if (dst_reg->smin_value >= 0 && smin_val >= 0) { + /* XORing two positive sign numbers gives a positive, + * so safe to cast u64 result into s64. + */ + dst_reg->smin_value = dst_reg->umin_value; + dst_reg->smax_value = dst_reg->umax_value; + } else { + dst_reg->smin_value = S64_MIN; + dst_reg->smax_value = S64_MAX; + } + + __update_reg_bounds(dst_reg); +} + static void __scalar32_min_max_lsh(struct bpf_reg_state *dst_reg, u64 umin_val, u64 umax_val) { @@ -6137,6 +6198,11 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env, scalar32_min_max_or(dst_reg, &src_reg); scalar_min_max_or(dst_reg, &src_reg); break; + case BPF_XOR: + dst_reg->var_off = tnum_xor(dst_reg->var_off, src_reg.var_off); + scalar32_min_max_xor(dst_reg, &src_reg); + scalar_min_max_xor(dst_reg, &src_reg); + break; case BPF_LSH: if (umax_val >= insn_bitness) { /* Shifts greater than 31 or 63 are undefined. |