diff mbox series

[bpf-next,2/2] selftests/bpf: Add a couple of tests for potential sdiv overflow

Message ID 20240911044022.2262427-1-yonghong.song@linux.dev (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series [bpf-next,1/2] bpf: Fix a sdiv overflow issue | expand

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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: 7 this patch: 7
netdev/build_tools success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers warning 11 maintainers not CCed: sdf@fomichev.me mykolal@fb.com eddyz87@gmail.com haoluo@google.com jolsa@kernel.org shuah@kernel.org linux-kselftest@vger.kernel.org song@kernel.org kpsingh@kernel.org martin.lau@linux.dev john.fastabend@gmail.com
netdev/build_clang success Errors and warnings before: 7 this patch: 7
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: 7 this patch: 7
netdev/checkpatch fail CHECK: spaces preferred around that '%' (ctx:WxV) CHECK: spaces preferred around that '+' (ctx:VxV) CHECK: spaces preferred around that '+' (ctx:WxV) CHECK: spaces preferred around that '-' (ctx:WxV) CHECK: spaces preferred around that '/' (ctx:VxO) ERROR: space required before that '-' (ctx:OxV) ERROR: spaces required around that '/=' (ctx:VxW) ERROR: spaces required around that ':' (ctx:VxW) WARNING: Avoid line continuations in quoted strings WARNING: Avoid unnecessary line continuations
netdev/build_clang_rust success No Rust files in patch. Skipping build
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Commit Message

Yonghong Song Sept. 11, 2024, 4:40 a.m. UTC 
Two subtests are added to exercise the patched code which handles
LLONG_MIN/-1. The first subtest will cause kernel exception without
previous kernel verifier change. The second subtest exercises part
of the patched code logic and the end result is still correct.

Translated asm codes are parts of correctness checking and those asm
codes also make it easy to understand the patched code in verifier.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
 .../selftests/bpf/progs/verifier_sdiv.c       | 69 +++++++++++++++++++
 1 file changed, 69 insertions(+)
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/progs/verifier_sdiv.c b/tools/testing/selftests/bpf/progs/verifier_sdiv.c
index 2a2271cf0294..c9c56008e534 100644
--- a/tools/testing/selftests/bpf/progs/verifier_sdiv.c
+++ b/tools/testing/selftests/bpf/progs/verifier_sdiv.c
@@ -1,6 +1,7 @@ 
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/bpf.h>
+#include <limits.h>
 #include <bpf/bpf_helpers.h>
 #include "bpf_misc.h"
 
@@ -770,6 +771,74 @@  __naked void smod64_zero_divisor(void)
 "	::: __clobber_all);
 }
 
+SEC("socket")
+__description("SDIV64, overflow, LLONG_MIN/-1")
+__success __retval(1)
+__arch_x86_64
+__xlated("0: r2 = 0x8000000000000000")
+__xlated("2: r3 = -1")
+__xlated("3: r4 = r2")
+__xlated("4: if r3 != 0x0 goto pc+2")
+__xlated("5: w2 ^= w2")
+__xlated("6: goto pc+8")
+__xlated("7: if r3 != 0xffffffff goto pc+6")
+__xlated("8: r3 = 0x8000000000000000")
+__xlated("10: if r2 != r3 goto pc+2")
+__xlated("11: r3 = -1")
+__xlated("12: goto pc+2")
+__xlated("13: r3 = -1")
+__xlated("14: r2 s/= r3")
+__xlated("15: r0 = 0")
+__xlated("16: if r2 != r4 goto pc+1")
+__xlated("17: r0 = 1")
+__xlated("18: exit")
+__naked void sdiv64_overflow(void)
+{
+	asm volatile ("					\
+	r2 = %[llong_min] ll;				\
+	r3 = -1;					\
+	r4 = r2;					\
+	r2 s/= r3;					\
+	r0 = 0;						\
+	if r2 != r4 goto +1;				\
+	r0 = 1;						\
+	exit;						\
+"	:
+	: __imm_const(llong_min, LLONG_MIN)
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("SDIV64, divisor -1")
+__success __retval(-5)
+__arch_x86_64
+__xlated("0: r2 = 5")
+__xlated("1: r3 = -1")
+__xlated("2: if r3 != 0x0 goto pc+2")
+__xlated("3: w2 ^= w2")
+__xlated("4: goto pc+8")
+__xlated("5: if r3 != 0xffffffff goto pc+6")
+__xlated("6: r3 = 0x8000000000000000")
+__xlated("8: if r2 != r3 goto pc+2")
+__xlated("9: r3 = -1")
+__xlated("10: goto pc+2")
+__xlated("11: r3 = -1")
+__xlated("12: r2 s/= r3")
+__xlated("13: r0 = r2")
+__xlated("14: exit")
+__naked void sdiv64_divisor_neg_1(void)
+{
+	asm volatile ("					\
+	r2 = 5;						\
+	r3 = -1;					\
+	r2 s/= r3;					\
+	r0 = r2;					\
+	exit;						\
+"	:
+	: __imm_const(llong_min, LLONG_MIN)
+	: __clobber_all);
+}
+
 #else
 
 SEC("socket")