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[bpf-next,v3,11/12] selftests/bpf: Add dynptr partial slot overwrite tests

Message ID 20230120034314.1921848-12-memxor@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series Dynptr fixes | expand

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Commit Message

Kumar Kartikeya Dwivedi Jan. 20, 2023, 3:43 a.m. UTC 
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@gmail.com>
---
 .../testing/selftests/bpf/progs/dynptr_fail.c | 66 +++++++++++++++++++
 1 file changed, 66 insertions(+)
diff mbox series

Patch

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;
+}