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Message-ID: <20231220214013.3327288-16-maxtram95@gmail.com>
Date: Wed, 20 Dec 2023 23:40:13 +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>
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 15/15] selftests/bpf: states pruning checks for scalar vs STACK_{MISC,ZERO}
From: Eduard Zingerman <eddyz87@...il.com>
Check that stacksafe() considers the following old vs cur stack spill
state combinations equivalent:
- spill of unbound scalar vs combination of STACK_{MISC,ZERO,INVALID}
- STACK_MISC vs spill of unbound scalar
- spill of scalar 0 vs STACK_ZERO
- STACK_ZERO vs spill of scalar 0
Signed-off-by: Eduard Zingerman <eddyz87@...il.com>
---
.../selftests/bpf/progs/verifier_spill_fill.c | 192 ++++++++++++++++++
1 file changed, 192 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
index df195cf5c77b..e2acc4fc3d10 100644
--- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
+++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
@@ -1046,4 +1046,196 @@ l0_%=: r1 >>= 32; \
: __clobber_all);
}
+/* stacksafe(): check if spill of unbound scalar in old state is
+ * considered equivalent to any state of the spill in the current state.
+ *
+ * On the first verification path an unbound scalar is written for
+ * fp-8 and later marked precise.
+ * On the second verification path a mix of STACK_MISC/ZERO/INVALID is
+ * written to fp-8. These should be considered equivalent.
+ */
+SEC("socket")
+__success __log_level(2)
+__msg("10: (79) r0 = *(u64 *)(r10 -8)")
+__msg("10: safe")
+__msg("processed 16 insns")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void old_unbound_scalar_vs_cur_anything(void)
+{
+ asm volatile(
+ /* get a random value for branching */
+ "call %[bpf_ktime_get_ns];"
+ "r7 = r0;"
+ /* get a random value for storing at fp-8 */
+ "call %[bpf_ktime_get_ns];"
+ "if r7 == 0 goto 1f;"
+ /* unbound scalar written to fp-8 */
+ "*(u64*)(r10 - 8) = r0;"
+ "goto 2f;"
+"1:"
+ /* mark fp-8 as mix of STACK_MISC/ZERO/INVALID */
+ "r1 = 0;"
+ "*(u8*)(r10 - 8) = r0;"
+ "*(u8*)(r10 - 7) = r1;"
+ /* fp-2..fp-6 remain STACK_INVALID */
+ "*(u8*)(r10 - 1) = r0;"
+"2:"
+ /* read fp-8 and force it precise, should be considered safe
+ * on second visit
+ */
+ "r0 = *(u64*)(r10 - 8);"
+ "r0 &= 0xff;"
+ "r1 = r10;"
+ "r1 += r0;"
+ "exit;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
+/* stacksafe(): check if STACK_MISC in old state is considered
+ * equivalent to stack spill of unbound scalar in cur state.
+ */
+SEC("socket")
+__success __log_level(2)
+__msg("8: (79) r0 = *(u64 *)(r10 -8) ; R0_w=scalar(id=1) R10=fp0 fp-8=scalar(id=1)")
+__msg("8: safe")
+__msg("processed 11 insns")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void old_unbound_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 unbound scalar at fp-8 */
+ "call %[bpf_ktime_get_ns];"
+ "*(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 be considered safe on second visit */
+ "r0 = *(u64*)(r10 - 8);"
+ "exit;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
+/* stacksafe(): check if stack spill of unbound scalar in old state is
+ * considered equivalent to STACK_MISC in cur state.
+ */
+SEC("socket")
+__success __log_level(2)
+__msg("8: (79) r0 = *(u64 *)(r10 -8) ; R0_w=scalar() R10=fp0 fp-8=mmmmmmmm")
+__msg("8: safe")
+__msg("processed 11 insns")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void old_stack_misc_vs_cur_unbound_scalar(void)
+{
+ asm volatile(
+ /* 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 unbound scalar at fp-8 */
+ "call %[bpf_ktime_get_ns];"
+ "*(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 if spill of register with value 0 in old state
+ * is considered equivalent to STACK_ZERO.
+ */
+SEC("socket")
+__success __log_level(2)
+__msg("9: (79) r0 = *(u64 *)(r10 -8)")
+__msg("9: safe")
+__msg("processed 15 insns")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void old_spill_zero_vs_stack_zero(void)
+{
+ asm volatile(
+ /* get a random value for branching */
+ "call %[bpf_ktime_get_ns];"
+ "r7 = r0;"
+ /* get a random value for storing at fp-8 */
+ "call %[bpf_ktime_get_ns];"
+ "if r7 == 0 goto 1f;"
+ /* conjure spilled register with value 0 at fp-8 */
+ "*(u64*)(r10 - 8) = r0;"
+ "if r0 != 0 goto 3f;"
+ "goto 2f;"
+"1:"
+ /* conjure STACK_ZERO at fp-8 */
+ "r1 = 0;"
+ "*(u64*)(r10 - 8) = r1;"
+"2:"
+ /* read fp-8 and force it precise, should be considered safe
+ * on second visit
+ */
+ "r0 = *(u64*)(r10 - 8);"
+ "r1 = r10;"
+ "r1 += r0;"
+"3:"
+ "exit;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
+/* stacksafe(): similar to old_spill_zero_vs_stack_zero() but the
+ * other way around: check if STACK_ZERO is considered equivalent to
+ * spill of register with value 0.
+ */
+SEC("socket")
+__success __log_level(2)
+__msg("8: (79) r0 = *(u64 *)(r10 -8)")
+__msg("8: safe")
+__msg("processed 14 insns")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void old_stack_zero_vs_spill_zero(void)
+{
+ asm volatile(
+ /* get a random value for branching */
+ "call %[bpf_ktime_get_ns];"
+ "if r0 == 0 goto 1f;"
+ /* conjure STACK_ZERO at fp-8 */
+ "r1 = 0;"
+ "*(u64*)(r10 - 8) = r1;"
+ "goto 2f;"
+"1:"
+ /* conjure spilled register with value 0 at fp-8 */
+ "call %[bpf_ktime_get_ns];"
+ "*(u64*)(r10 - 8) = r0;"
+ "if r0 != 0 goto 3f;"
+"2:"
+ /* read fp-8 and force it precise, should be considered safe
+ * on second visit
+ */
+ "r0 = *(u64*)(r10 - 8);"
+ "r1 = r10;"
+ "r1 += r0;"
+"3:"
+ "exit;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
char _license[] SEC("license") = "GPL";
--
2.42.1
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