From: Maxim Mikityanskiy <maxim@xxxxxxxxxxxxx>
The previous commit allowed to preserve boundaries and track IDs of
scalars on narrowing fills. Add test cases for that pattern.
Signed-off-by: Maxim Mikityanskiy <maxim@xxxxxxxxxxxxx>
---
.../selftests/bpf/progs/verifier_spill_fill.c | 108 ++++++++++++++++++
1 file changed, 108 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
index de03e72e07a9..df195cf5c77b 100644
--- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
+++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
@@ -938,4 +938,112 @@ l0_%=: r0 = 0; \
: __clobber_all);
}
+SEC("xdp")
+__description("32-bit fill after 64-bit spill")
+__success __retval(0)
+__naked void fill_32bit_after_spill_64bit(void)
+{
+ asm volatile(" \
+ /* Randomize the upper 32 bits. */ \
+ call %[bpf_get_prandom_u32]; \
+ r0 <<= 32; \
+ /* 64-bit spill r0 to stack. */ \
+ *(u64*)(r10 - 8) = r0; \
+ /* 32-bit fill r0 from stack. */ \
+ r0 = *(u32*)(r10 - %[offset]); \
+ /* Boundary check on r0 with predetermined result. */\
+ if r0 == 0 goto l0_%=; \
+ /* Dead branch: the verifier should prune it. Do an invalid memory\
+ * access if the verifier follows it. \
+ */ \
+ r0 = *(u64*)(r9 + 0); \
+l0_%=: exit; \
+" :
+ : __imm(bpf_get_prandom_u32),
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ __imm_const(offset, 8)
+#else
+ __imm_const(offset, 4)
+#endif
+ : __clobber_all);
+}
+
+SEC("xdp")
+__description("32-bit fill after 64-bit spill of 32-bit value should preserve ID")
+__success __retval(0)
+__naked void fill_32bit_after_spill_64bit_preserve_id(void)
+{
+ asm volatile (" \
+ /* Randomize the lower 32 bits. */ \
+ call %[bpf_get_prandom_u32]; \
+ w0 &= 0xffffffff; \
+ /* 64-bit spill r0 to stack - should assign an ID. */\
+ *(u64*)(r10 - 8) = r0; \
+ /* 32-bit fill r1 from stack - should preserve the ID. */\
+ r1 = *(u32*)(r10 - %[offset]); \
+ /* Compare r1 with another register to trigger find_equal_scalars. */\
+ r2 = 0; \
+ if r1 != r2 goto l0_%=; \
+ /* The result of this comparison is predefined. */\
+ if r0 == r2 goto l0_%=; \
+ /* Dead branch: the verifier should prune it. Do an invalid memory\
+ * access if the verifier follows it. \
+ */ \
+ r0 = *(u64*)(r9 + 0); \
+ exit; \
+l0_%=: r0 = 0; \
+ exit; \
+" :
+ : __imm(bpf_get_prandom_u32),
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ __imm_const(offset, 8)
+#else
+ __imm_const(offset, 4)
+#endif
+ : __clobber_all);
+}
+
+SEC("xdp")
+__description("32-bit fill after 64-bit spill should clear ID")
+__failure __msg("math between ctx pointer and 4294967295 is not allowed")
+__naked void fill_32bit_after_spill_64bit_clear_id(void)
+{
+ asm volatile (" \
+ r6 = r1; \
+ /* Roll one bit to force the verifier to track both branches. */\
+ call %[bpf_get_prandom_u32]; \
+ r0 &= 0x8; \
+ /* Put a large number into r1. */ \
+ r1 = 0xffffffff; \
+ r1 <<= 32; \
+ r1 += r0; \
+ /* 64-bit spill r1 to stack - should assign an ID. */\
+ *(u64*)(r10 - 8) = r1; \
+ /* 32-bit fill r2 from stack - should clear the ID. */\
+ r2 = *(u32*)(r10 - %[offset]); \
+ /* Compare r2 with another register to trigger find_equal_scalars.\
+ * Having one random bit is important here, otherwise the verifier cuts\
+ * the corners. If the ID was mistakenly preserved on fill, this would\
+ * cause the verifier to think that r1 is also equal to zero in one of\
+ * the branches, and equal to eight on the other branch.\
+ */ \
+ r3 = 0; \
+ if r2 != r3 goto l0_%=; \
+l0_%=: r1 >>= 32; \
+ /* The verifier shouldn't propagate r2's range to r1, so it should\
+ * still remember r1 = 0xffffffff and reject the below.\
+ */ \
+ r6 += r1; \
+ r0 = *(u32*)(r6 + 0); \
+ exit; \
+" :
+ : __imm(bpf_get_prandom_u32),
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ __imm_const(offset, 8)
+#else
+ __imm_const(offset, 4)
+#endif
+ : __clobber_all);
+}
+
char _license[] SEC("license") = "GPL";
--
2.42.1
