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authorDavid S. Miller <davem@davemloft.net>2017-07-24 14:02:55 -0700
committerDavid S. Miller <davem@davemloft.net>2017-07-24 14:02:55 -0700
commit1d9b86de3776aa0e809745e5c9e272b79a7ac09b (patch)
treed90dcd6dc8670134778a891336b3b3c29f86c51a
parent70dba204a396c1c094749c4ef9bd27d5e8176a08 (diff)
parent9305706c2e808ae59f1eb201867f82f1ddf6d7a6 (diff)
Merge branch 'bpf-fix-verifier-min-max-handling-in-BPF_SUB'
Edward Cree says: ==================== bpf: fix verifier min/max handling in BPF_SUB I managed to come up with a test for the swapped bounds in BPF_SUB, so here it is along with a patch that fixes it, separated out from my 'rewrite everything' series so it can go to -stable. ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--kernel/bpf/verifier.c21
-rw-r--r--tools/testing/selftests/bpf/test_verifier.c28
2 files changed, 43 insertions, 6 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index af9e84a4944e..664d93972373 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1865,10 +1865,12 @@ static void adjust_reg_min_max_vals(struct bpf_verifier_env *env,
* do our normal operations to the register, we need to set the values
* to the min/max since they are undefined.
*/
- if (min_val == BPF_REGISTER_MIN_RANGE)
- dst_reg->min_value = BPF_REGISTER_MIN_RANGE;
- if (max_val == BPF_REGISTER_MAX_RANGE)
- dst_reg->max_value = BPF_REGISTER_MAX_RANGE;
+ if (opcode != BPF_SUB) {
+ if (min_val == BPF_REGISTER_MIN_RANGE)
+ dst_reg->min_value = BPF_REGISTER_MIN_RANGE;
+ if (max_val == BPF_REGISTER_MAX_RANGE)
+ dst_reg->max_value = BPF_REGISTER_MAX_RANGE;
+ }
switch (opcode) {
case BPF_ADD:
@@ -1879,10 +1881,17 @@ static void adjust_reg_min_max_vals(struct bpf_verifier_env *env,
dst_reg->min_align = min(src_align, dst_align);
break;
case BPF_SUB:
+ /* If one of our values was at the end of our ranges, then the
+ * _opposite_ value in the dst_reg goes to the end of our range.
+ */
+ if (min_val == BPF_REGISTER_MIN_RANGE)
+ dst_reg->max_value = BPF_REGISTER_MAX_RANGE;
+ if (max_val == BPF_REGISTER_MAX_RANGE)
+ dst_reg->min_value = BPF_REGISTER_MIN_RANGE;
if (dst_reg->min_value != BPF_REGISTER_MIN_RANGE)
- dst_reg->min_value -= min_val;
+ dst_reg->min_value -= max_val;
if (dst_reg->max_value != BPF_REGISTER_MAX_RANGE)
- dst_reg->max_value -= max_val;
+ dst_reg->max_value -= min_val;
dst_reg->min_align = min(src_align, dst_align);
break;
case BPF_MUL:
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index af7d173910f4..addea82f76c9 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -5980,6 +5980,34 @@ static struct bpf_test tests[] = {
.result = REJECT,
.result_unpriv = REJECT,
},
+ {
+ "subtraction bounds (map value)",
+ .insns = {
+ BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+ BPF_FUNC_map_lookup_elem),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 9),
+ BPF_LDX_MEM(BPF_B, BPF_REG_1, BPF_REG_0, 0),
+ BPF_JMP_IMM(BPF_JGT, BPF_REG_1, 0xff, 7),
+ BPF_LDX_MEM(BPF_B, BPF_REG_3, BPF_REG_0, 1),
+ BPF_JMP_IMM(BPF_JGT, BPF_REG_3, 0xff, 5),
+ BPF_ALU64_REG(BPF_SUB, BPF_REG_1, BPF_REG_3),
+ BPF_ALU64_IMM(BPF_RSH, BPF_REG_1, 56),
+ BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1),
+ BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map1 = { 3 },
+ .errstr_unpriv = "R0 pointer arithmetic prohibited",
+ .errstr = "R0 min value is negative, either use unsigned index or do a if (index >=0) check.",
+ .result = REJECT,
+ .result_unpriv = REJECT,
+ },
};
static int probe_filter_length(const struct bpf_insn *fp)