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-rw-r--r--kernel/bpf/verifier.c106
-rw-r--r--tools/testing/selftests/bpf/progs/verifier_bounds.c63
2 files changed, 104 insertions, 65 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7360f04f9ec7..9e3aba08984e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13878,6 +13878,46 @@ static void scalar_min_max_arsh(struct bpf_reg_state *dst_reg,
__update_reg_bounds(dst_reg);
}
+static bool is_safe_to_compute_dst_reg_range(struct bpf_insn *insn,
+ const struct bpf_reg_state *src_reg)
+{
+ bool src_is_const = false;
+ u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32;
+
+ if (insn_bitness == 32) {
+ if (tnum_subreg_is_const(src_reg->var_off)
+ && src_reg->s32_min_value == src_reg->s32_max_value
+ && src_reg->u32_min_value == src_reg->u32_max_value)
+ src_is_const = true;
+ } else {
+ if (tnum_is_const(src_reg->var_off)
+ && src_reg->smin_value == src_reg->smax_value
+ && src_reg->umin_value == src_reg->umax_value)
+ src_is_const = true;
+ }
+
+ switch (BPF_OP(insn->code)) {
+ case BPF_ADD:
+ case BPF_SUB:
+ case BPF_AND:
+ case BPF_XOR:
+ case BPF_OR:
+ case BPF_MUL:
+ return true;
+
+ /* Shift operators range is only computable if shift dimension operand
+ * is a constant. Shifts greater than 31 or 63 are undefined. This
+ * includes shifts by a negative number.
+ */
+ case BPF_LSH:
+ case BPF_RSH:
+ case BPF_ARSH:
+ return (src_is_const && src_reg->umax_value < insn_bitness);
+ default:
+ return false;
+ }
+}
+
/* WARNING: This function does calculations on 64-bit values, but the actual
* execution may occur on 32-bit values. Therefore, things like bitshifts
* need extra checks in the 32-bit case.
@@ -13887,53 +13927,11 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
struct bpf_reg_state *dst_reg,
struct bpf_reg_state src_reg)
{
- struct bpf_reg_state *regs = cur_regs(env);
u8 opcode = BPF_OP(insn->code);
- bool src_known;
- s64 smin_val, smax_val;
- u64 umin_val, umax_val;
- s32 s32_min_val, s32_max_val;
- u32 u32_min_val, u32_max_val;
- u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32;
bool alu32 = (BPF_CLASS(insn->code) != BPF_ALU64);
int ret;
- smin_val = src_reg.smin_value;
- smax_val = src_reg.smax_value;
- umin_val = src_reg.umin_value;
- umax_val = src_reg.umax_value;
-
- s32_min_val = src_reg.s32_min_value;
- s32_max_val = src_reg.s32_max_value;
- u32_min_val = src_reg.u32_min_value;
- u32_max_val = src_reg.u32_max_value;
-
- if (alu32) {
- src_known = tnum_subreg_is_const(src_reg.var_off);
- if ((src_known &&
- (s32_min_val != s32_max_val || u32_min_val != u32_max_val)) ||
- s32_min_val > s32_max_val || u32_min_val > u32_max_val) {
- /* Taint dst register if offset had invalid bounds
- * derived from e.g. dead branches.
- */
- __mark_reg_unknown(env, dst_reg);
- return 0;
- }
- } else {
- src_known = tnum_is_const(src_reg.var_off);
- if ((src_known &&
- (smin_val != smax_val || umin_val != umax_val)) ||
- smin_val > smax_val || umin_val > umax_val) {
- /* Taint dst register if offset had invalid bounds
- * derived from e.g. dead branches.
- */
- __mark_reg_unknown(env, dst_reg);
- return 0;
- }
- }
-
- if (!src_known &&
- opcode != BPF_ADD && opcode != BPF_SUB && opcode != BPF_AND) {
+ if (!is_safe_to_compute_dst_reg_range(insn, &src_reg)) {
__mark_reg_unknown(env, dst_reg);
return 0;
}
@@ -13990,46 +13988,24 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
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.
- * This includes shifts by a negative number.
- */
- mark_reg_unknown(env, regs, insn->dst_reg);
- break;
- }
if (alu32)
scalar32_min_max_lsh(dst_reg, &src_reg);
else
scalar_min_max_lsh(dst_reg, &src_reg);
break;
case BPF_RSH:
- if (umax_val >= insn_bitness) {
- /* Shifts greater than 31 or 63 are undefined.
- * This includes shifts by a negative number.
- */
- mark_reg_unknown(env, regs, insn->dst_reg);
- break;
- }
if (alu32)
scalar32_min_max_rsh(dst_reg, &src_reg);
else
scalar_min_max_rsh(dst_reg, &src_reg);
break;
case BPF_ARSH:
- if (umax_val >= insn_bitness) {
- /* Shifts greater than 31 or 63 are undefined.
- * This includes shifts by a negative number.
- */
- mark_reg_unknown(env, regs, insn->dst_reg);
- break;
- }
if (alu32)
scalar32_min_max_arsh(dst_reg, &src_reg);
else
scalar_min_max_arsh(dst_reg, &src_reg);
break;
default:
- mark_reg_unknown(env, regs, insn->dst_reg);
break;
}
diff --git a/tools/testing/selftests/bpf/progs/verifier_bounds.c b/tools/testing/selftests/bpf/progs/verifier_bounds.c
index 960998f16306..a0bb7fb40ea5 100644
--- a/tools/testing/selftests/bpf/progs/verifier_bounds.c
+++ b/tools/testing/selftests/bpf/progs/verifier_bounds.c
@@ -886,6 +886,69 @@ l1_%=: r0 = 0; \
}
SEC("socket")
+__description("bounds check for non const xor src dst")
+__success __log_level(2)
+__msg("5: (af) r0 ^= r6 ; R0_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=431,var_off=(0x0; 0x1af))")
+__naked void non_const_xor_src_dst(void)
+{
+ asm volatile (" \
+ call %[bpf_get_prandom_u32]; \
+ r6 = r0; \
+ call %[bpf_get_prandom_u32]; \
+ r6 &= 0xaf; \
+ r0 &= 0x1a0; \
+ r0 ^= r6; \
+ exit; \
+" :
+ : __imm(bpf_map_lookup_elem),
+ __imm_addr(map_hash_8b),
+ __imm(bpf_get_prandom_u32)
+ : __clobber_all);
+}
+
+SEC("socket")
+__description("bounds check for non const or src dst")
+__success __log_level(2)
+__msg("5: (4f) r0 |= r6 ; R0_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=431,var_off=(0x0; 0x1af))")
+__naked void non_const_or_src_dst(void)
+{
+ asm volatile (" \
+ call %[bpf_get_prandom_u32]; \
+ r6 = r0; \
+ call %[bpf_get_prandom_u32]; \
+ r6 &= 0xaf; \
+ r0 &= 0x1a0; \
+ r0 |= r6; \
+ exit; \
+" :
+ : __imm(bpf_map_lookup_elem),
+ __imm_addr(map_hash_8b),
+ __imm(bpf_get_prandom_u32)
+ : __clobber_all);
+}
+
+SEC("socket")
+__description("bounds check for non const mul regs")
+__success __log_level(2)
+__msg("5: (2f) r0 *= r6 ; R0_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=3825,var_off=(0x0; 0xfff))")
+__naked void non_const_mul_regs(void)
+{
+ asm volatile (" \
+ call %[bpf_get_prandom_u32]; \
+ r6 = r0; \
+ call %[bpf_get_prandom_u32]; \
+ r6 &= 0xff; \
+ r0 &= 0x0f; \
+ r0 *= r6; \
+ exit; \
+" :
+ : __imm(bpf_map_lookup_elem),
+ __imm_addr(map_hash_8b),
+ __imm(bpf_get_prandom_u32)
+ : __clobber_all);
+}
+
+SEC("socket")
__description("bounds checks after 32-bit truncation. test 1")
__success __failure_unpriv __msg_unpriv("R0 leaks addr")
__retval(0)
generated by cgit (git 2.34.1) at 2026-01-02 13:02:31 +0000