@@ -5134,12 +5134,6 @@ static bool stacksafe(struct bpf_func_state *old,
{
int i, spi;
- /* if explored stack has more populated slots than current stack
- * such stacks are not equivalent
- */
- if (old->allocated_stack > cur->allocated_stack)
- return false;
-
/* walk slots of the explored stack and ignore any additional
* slots in the current stack, since explored(safe) state
* didn't use them
@@ -5155,6 +5149,13 @@ static bool stacksafe(struct bpf_func_state *old,
if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_INVALID)
continue;
+
+ /* explored stack has more populated slots than current stack
+ * and these slots were used
+ */
+ if (i >= cur->allocated_stack)
+ return false;
+
/* if old state was safe with misc data in the stack
* it will be safe with zero-initialized stack.
* The opposite is not true
@@ -13647,6 +13647,28 @@ static struct bpf_test tests[] = {
.prog_type = BPF_PROG_TYPE_SCHED_CLS,
.result = ACCEPT,
},
+ {
+ "allocated_stack",
+ .insns = {
+ BPF_ALU64_REG(BPF_MOV, BPF_REG_6, BPF_REG_1),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_get_prandom_u32),
+ BPF_ALU64_REG(BPF_MOV, BPF_REG_7, BPF_REG_0),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 5),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_6, -8),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_10, -8),
+ BPF_STX_MEM(BPF_B, BPF_REG_10, BPF_REG_7, -9),
+ BPF_LDX_MEM(BPF_B, BPF_REG_7, BPF_REG_10, -9),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 0),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 0),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 0),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ .result_unpriv = ACCEPT,
+ .insn_processed = 15,
+ },
{
"reference tracking in call: free reference in subprog and outside",
.insns = {
if (old->allocated_stack > cur->allocated_stack) check is too conservative. In some cases explored stack could have allocated more space, but that stack space was not live. The test case improves from 19 to 15 processed insns and improvement on real programs is significant as well: before after bpf_lb-DLB_L3.o 1940 1831 bpf_lb-DLB_L4.o 3089 3029 bpf_lb-DUNKNOWN.o 1065 1064 bpf_lxc-DDROP_ALL.o 28052 26309 bpf_lxc-DUNKNOWN.o 35487 33517 bpf_netdev.o 10864 9713 bpf_overlay.o 6643 6184 bpf_lcx_jit.o 38437 37335 Signed-off-by: Alexei Starovoitov <ast@kernel.org> --- kernel/bpf/verifier.c | 13 ++++++------ tools/testing/selftests/bpf/test_verifier.c | 22 +++++++++++++++++++++ 2 files changed, 29 insertions(+), 6 deletions(-)