Try creating a dynptr, then overwriting second slot with first slot of
another dynptr. Then, the first slot of first dynptr should also be
invalidated, but without our fix that does not happen. As a consequence,
the unfixed case allows passing first dynptr (as the kernel check only
checks for slot_type and then first_slot == true).
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
---
.../testing/selftests/bpf/progs/dynptr_fail.c | 66 +++++++++++++++++++
1 file changed, 66 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index 9477c238af57..cf2d12329a1e 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c
@@ -834,3 +834,69 @@ int dynptr_var_off_overwrite(struct __sk_buff *ctx)
);
return 0;
}
+
+SEC("?tc")
+__failure __msg("cannot overwrite referenced dynptr") __log_level(2)
+int dynptr_partial_slot_invalidate(struct __sk_buff *ctx)
+{
+ asm volatile (
+ "r6 = %[ringbuf] ll;"
+ "r7 = %[array_map4] ll;"
+ "r1 = r7;"
+ "r2 = r10;"
+ "r2 += -8;"
+ "r9 = 0;"
+ "*(u64 *)(r2 + 0) = r9;"
+ "r3 = r2;"
+ "r4 = 0;"
+ "r8 = r2;"
+ "call %[bpf_map_update_elem];"
+ "r1 = r7;"
+ "r2 = r8;"
+ "call %[bpf_map_lookup_elem];"
+ "if r0 != 0 goto sjmp1;"
+ "exit;"
+ "sjmp1:"
+ "r7 = r0;"
+ "r1 = r6;"
+ "r2 = 8;"
+ "r3 = 0;"
+ "r4 = r10;"
+ "r4 += -24;"
+ "call %[bpf_ringbuf_reserve_dynptr];"
+ "*(u64 *)(r10 - 16) = r9;"
+ "r1 = r7;"
+ "r2 = 8;"
+ "r3 = 0;"
+ "r4 = r10;"
+ "r4 += -16;"
+ "call %[bpf_dynptr_from_mem];"
+ "r1 = r10;"
+ "r1 += -512;"
+ "r2 = 488;"
+ "r3 = r10;"
+ "r3 += -24;"
+ "r4 = 0;"
+ "r5 = 0;"
+ "call %[bpf_dynptr_read];"
+ "r8 = 1;"
+ "if r0 != 0 goto sjmp2;"
+ "r8 = 0;"
+ "sjmp2:"
+ "r1 = r10;"
+ "r1 += -24;"
+ "r2 = 0;"
+ "call %[bpf_ringbuf_discard_dynptr];"
+ :
+ : __imm(bpf_map_update_elem),
+ __imm(bpf_map_lookup_elem),
+ __imm(bpf_ringbuf_reserve_dynptr),
+ __imm(bpf_ringbuf_discard_dynptr),
+ __imm(bpf_dynptr_from_mem),
+ __imm(bpf_dynptr_read),
+ __imm_addr(ringbuf),
+ __imm_addr(array_map4)
+ : __clobber_all
+ );
+ return 0;
+}
--
2.39.1
