diff mbox series

[bpf-next,10/10] selftests/bpf: adjust global_func15 test to validate prog exit precision

Message ID 20231122011656.1105943-11-andrii@kernel.org (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series BPF verifier retval logic fixes | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR success PR summary
netdev/series_format success Posting correctly formatted
netdev/codegen success Generated files up to date
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 8 this patch: 8
netdev/cc_maintainers warning 11 maintainers not CCed: mykolal@fb.com yonghong.song@linux.dev song@kernel.org haoluo@google.com linux-kselftest@vger.kernel.org martin.lau@linux.dev jolsa@kernel.org kpsingh@kernel.org john.fastabend@gmail.com shuah@kernel.org sdf@google.com
netdev/build_clang success Errors and warnings before: 8 this patch: 8
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 8 this patch: 8
netdev/checkpatch warning CHECK: Lines should not end with a '(' WARNING: Prefer 'fallthrough;' over fallthrough comment WARNING: quoted string split across lines
netdev/build_clang_rust success No Rust files in patch. Skipping build
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Commit Message

Andrii Nakryiko Nov. 22, 2023, 1:16 a.m. UTC 
Add one more subtest to  global_func15 selftest to validate that
verifier properly marks r0 as precise and avoids erroneous state pruning
of the branch that has return value outside of expected [0, 1] value.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 .../selftests/bpf/progs/test_global_func15.c  | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)

Comments

Eduard Zingerman Nov. 22, 2023, 3:13 p.m. UTC | #1 
On Tue, 2023-11-21 at 17:16 -0800, Andrii Nakryiko wrote:
> > Add one more subtest to  global_func15 selftest to validate that
> > verifier properly marks r0 as precise and avoids erroneous state pruning
> > of the branch that has return value outside of expected [0, 1] value.
> > 
> > Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
> > ---

Acked-by: Eduard Zingerman <eddyz87@gmail.com>

[...]
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/progs/test_global_func15.c b/tools/testing/selftests/bpf/progs/test_global_func15.c
index f80207480e8a..fc24d1e1f287 100644
--- a/tools/testing/selftests/bpf/progs/test_global_func15.c
+++ b/tools/testing/selftests/bpf/progs/test_global_func15.c
@@ -22,3 +22,32 @@  int global_func15(struct __sk_buff *skb)
 
 	return v;
 }
+
+SEC("cgroup_skb/ingress")
+__failure __msg("At program exit the register R0 has ")
+__log_level(2) __flag(BPF_F_TEST_STATE_FREQ)
+__naked int global_func15_tricky_pruning(void)
+{
+	asm volatile (
+		"r0 = 1;"
+		"*(u64 *)(r10 -8) = r0;"
+		"call %[bpf_get_prandom_u32];"
+		"if r0 > 1000 goto 1f;"
+		"r0 = 1;"
+	"1:"
+		"goto +0;" /* checkpoint */
+		/* cgroup_skb/ingress program is expected to return [0, 1]
+		 * values, so branch above makes sure that in a fallthrough
+		 * case we have a valid 1 stored in R0 register, but in
+		 * a branch case we assign some random value to R0.  So if
+		 * there is something wrong with precision tracking for R0 at
+		 * program exit, we might erronenously prune branch case,
+		 * because R0 in fallthrough case is imprecise (and thus any
+		 * value is valid from POV of verifier is_state_equal() logic)
+		 */
+		"exit;"
+		:
+		: __imm(bpf_get_prandom_u32)
+		: __clobber_common
+	);
+}