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Message-ID: <20240127175237.526726-7-maxtram95@gmail.com>
Date: Sat, 27 Jan 2024 19:52:37 +0200
From: Maxim Mikityanskiy <maxtram95@...il.com>
To: Eduard Zingerman <eddyz87@...il.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Shung-Hsi Yu <shung-hsi.yu@...e.com>
Cc: John Fastabend <john.fastabend@...il.com>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>,
Mykola Lysenko <mykolal@...com>,
Shuah Khan <shuah@...nel.org>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Jesper Dangaard Brouer <hawk@...nel.org>,
bpf@...r.kernel.org,
linux-kselftest@...r.kernel.org,
netdev@...r.kernel.org
Subject: [PATCH bpf-next v3 6/6] selftests/bpf: states pruning checks for scalar vs STACK_MISC
From: Eduard Zingerman <eddyz87@...il.com>
Check that stacksafe() compares spilled scalars with STACK_MISC.
The following combinations are explored:
- old spill of imprecise scalar is equivalent to cur STACK_{MISC,INVALID}
(plus error in unpriv mode);
- old spill of precise scalar is not equivalent to cur STACK_MISC;
- old STACK_MISC is equivalent to cur scalar;
- old STACK_MISC is not equivalent to cur non-scalar.
Signed-off-by: Eduard Zingerman <eddyz87@...il.com>
---
.../selftests/bpf/progs/verifier_spill_fill.c | 154 ++++++++++++++++++
1 file changed, 154 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
index 7f3b1319bd99..85e48069c9e6 100644
--- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
+++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
@@ -1090,4 +1090,158 @@ l0_%=: r1 >>= 32; \
: __clobber_all);
}
+/* stacksafe(): check if stack spill of an imprecise scalar in old state
+ * is considered equivalent to STACK_{MISC,INVALID} in cur state.
+ */
+SEC("socket")
+__success __log_level(2)
+__msg("8: (79) r1 = *(u64 *)(r10 -8)")
+__msg("8: safe")
+__msg("processed 11 insns")
+/* STACK_INVALID should prevent verifier in unpriv mode from
+ * considering states equivalent and force an error on second
+ * verification path (entry - label 1 - label 2).
+ */
+__failure_unpriv
+__msg_unpriv("8: (79) r1 = *(u64 *)(r10 -8)")
+__msg_unpriv("9: (95) exit")
+__msg_unpriv("8: (79) r1 = *(u64 *)(r10 -8)")
+__msg_unpriv("invalid read from stack off -8+2 size 8")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void old_imprecise_scalar_vs_cur_stack_misc(void)
+{
+ asm volatile(
+ /* get a random value for branching */
+ "call %[bpf_ktime_get_ns];"
+ "if r0 == 0 goto 1f;"
+ /* conjure scalar at fp-8 */
+ "r0 = 42;"
+ "*(u64*)(r10 - 8) = r0;"
+ "goto 2f;"
+"1:"
+ /* conjure STACK_{MISC,INVALID} at fp-8 */
+ "call %[bpf_ktime_get_ns];"
+ "*(u16*)(r10 - 8) = r0;"
+ "*(u16*)(r10 - 4) = r0;"
+"2:"
+ /* read fp-8, should be considered safe on second visit */
+ "r1 = *(u64*)(r10 - 8);"
+ "exit;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
+/* stacksafe(): check that stack spill of a precise scalar in old state
+ * is not considered equivalent to STACK_MISC in cur state.
+ */
+SEC("socket")
+__success __log_level(2)
+/* verifier should visit 'if r1 == 0x2a ...' two times:
+ * - once for path entry - label 2;
+ * - once for path entry - label 1 - label 2.
+ */
+__msg("if r1 == 0x2a goto pc+0")
+__msg("if r1 == 0x2a goto pc+0")
+__msg("processed 15 insns")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void old_precise_scalar_vs_cur_stack_misc(void)
+{
+ asm volatile(
+ /* get a random value for branching */
+ "call %[bpf_ktime_get_ns];"
+ "if r0 == 0 goto 1f;"
+ /* conjure scalar at fp-8 */
+ "r0 = 42;"
+ "*(u64*)(r10 - 8) = r0;"
+ "goto 2f;"
+"1:"
+ /* conjure STACK_MISC at fp-8 */
+ "call %[bpf_ktime_get_ns];"
+ "*(u64*)(r10 - 8) = r0;"
+ "*(u32*)(r10 - 4) = r0;"
+"2:"
+ /* read fp-8, should not be considered safe on second visit */
+ "r1 = *(u64*)(r10 - 8);"
+ /* use r1 in precise context */
+ "if r1 == 42 goto +0;"
+ "exit;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
+/* stacksafe(): check if STACK_MISC in old state is considered
+ * equivalent to stack spill of a scalar in cur state.
+ */
+SEC("socket")
+__success __log_level(2)
+__msg("8: (79) r0 = *(u64 *)(r10 -8)")
+__msg("8: safe")
+__msg("processed 11 insns")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void old_stack_misc_vs_cur_scalar(void)
+{
+ asm volatile(
+ /* get a random value for branching */
+ "call %[bpf_ktime_get_ns];"
+ "if r0 == 0 goto 1f;"
+ /* conjure STACK_{MISC,INVALID} at fp-8 */
+ "call %[bpf_ktime_get_ns];"
+ "*(u16*)(r10 - 8) = r0;"
+ "*(u16*)(r10 - 4) = r0;"
+ "goto 2f;"
+"1:"
+ /* conjure scalar at fp-8 */
+ "r0 = 42;"
+ "*(u64*)(r10 - 8) = r0;"
+"2:"
+ /* read fp-8, should be considered safe on second visit */
+ "r0 = *(u64*)(r10 - 8);"
+ "exit;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
+/* stacksafe(): check that STACK_MISC in old state is not considered
+ * equivalent to stack spill of a non-scalar in cur state.
+ */
+SEC("socket")
+__success __log_level(2)
+/* verifier should process exit instructions twice:
+ * - once for path entry - label 2;
+ * - once for path entry - label 1 - label 2.
+ */
+__msg("r1 = *(u64 *)(r10 -8)")
+__msg("exit")
+__msg("r1 = *(u64 *)(r10 -8)")
+__msg("exit")
+__msg("processed 11 insns")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void old_stack_misc_vs_cur_ctx_ptr(void)
+{
+ asm volatile(
+ /* remember context pointer in r9 */
+ "r9 = r1;"
+ /* get a random value for branching */
+ "call %[bpf_ktime_get_ns];"
+ "if r0 == 0 goto 1f;"
+ /* conjure STACK_MISC at fp-8 */
+ "call %[bpf_ktime_get_ns];"
+ "*(u64*)(r10 - 8) = r0;"
+ "*(u32*)(r10 - 4) = r0;"
+ "goto 2f;"
+"1:"
+ /* conjure context pointer in fp-8 */
+ "*(u64*)(r10 - 8) = r9;"
+"2:"
+ /* read fp-8, should not be considered safe on second visit */
+ "r1 = *(u64*)(r10 - 8);"
+ "exit;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
char _license[] SEC("license") = "GPL";
--
2.43.0
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