From: Maxim Mikityanskiy <maxim@xxxxxxxxxxxxx>
When a range check is performed on a register that was 32-bit spilled to
the stack, the IDs of the two instances of the register are the same, so
the range should also be the same.
Signed-off-by: Maxim Mikityanskiy <maxim@xxxxxxxxxxxxx>
---
.../selftests/bpf/progs/verifier_spill_fill.c | 31 +++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
index 84eccab36582..f2c1fe5b1dba 100644
--- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
+++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
@@ -737,4 +737,35 @@ __naked void stack_load_preserves_const_precision_subreg(void)
: __clobber_common);
}
+SEC("xdp")
+__description("32-bit spilled reg range should be tracked")
+__success __retval(0)
+__naked void spill_32bit_range_track(void)
+{
+ asm volatile(" \
+ call %[bpf_ktime_get_ns]; \
+ /* Make r0 bounded. */ \
+ r0 &= 65535; \
+ /* Assign an ID to r0. */ \
+ r1 = r0; \
+ /* 32-bit spill r0 to stack. */ \
+ *(u32*)(r10 - 8) = r0; \
+ /* Boundary check on r0. */ \
+ if r0 < 1 goto l0_%=; \
+ /* 32-bit fill r1 from stack. */ \
+ r1 = *(u32*)(r10 - 8); \
+ /* r1 == r0 => r1 >= 1 always. */ \
+ if r1 >= 1 goto l0_%=; \
+ /* Dead branch: the verifier should prune it. \
+ * Do an invalid memory access if the verifier \
+ * follows it. \
+ */ \
+ r0 = *(u64*)(r9 + 0); \
+l0_%=: r0 = 0; \
+ exit; \
+" :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
char _license[] SEC("license") = "GPL";
--
2.42.1
