diff mbox series

[bpf,v4,2/2] selftests/bpf: Add test cases to assert proper ID tracking on spill

Message ID 20230607123951.558971-3-maxtram95@gmail.com (mailing list archive)
State Accepted
Delegated to: BPF
Headers show
Series Fix verifier id tracking of scalars on spill | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf
netdev/fixes_present success Fixes tag present in non-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 success CCed 21 of 21 maintainers
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 fail CHECK: spaces preferred around that '%' (ctx:WxV) CHECK: spaces preferred around that '-' (ctx:VxV) ERROR: "(foo*)" should be "(foo *)" ERROR: spaces required around that '%=' (ctx:VxO) ERROR: spaces required around that ':' (ctx:OxW) ERROR: spaces required around that '=' (ctx:VxV) WARNING: Avoid line continuations in quoted strings WARNING: Avoid unnecessary line continuations
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-PR success PR summary
bpf/vmtest-bpf-VM_Test-1 success Logs for ShellCheck
bpf/vmtest-bpf-VM_Test-2 success Logs for build for aarch64 with gcc
bpf/vmtest-bpf-VM_Test-4 success Logs for build for x86_64 with gcc
bpf/vmtest-bpf-VM_Test-5 success Logs for build for x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-6 success Logs for set-matrix
bpf/vmtest-bpf-VM_Test-3 success Logs for build for s390x with gcc
bpf/vmtest-bpf-VM_Test-25 success Logs for test_verifier on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-7 success Logs for test_maps on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-9 success Logs for test_maps on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-10 success Logs for test_maps on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-11 success Logs for test_progs on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-13 success Logs for test_progs on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-14 success Logs for test_progs on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-15 success Logs for test_progs_no_alu32 on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-17 success Logs for test_progs_no_alu32 on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-18 success Logs for test_progs_no_alu32 on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-19 success Logs for test_progs_no_alu32_parallel on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-20 success Logs for test_progs_no_alu32_parallel on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-21 success Logs for test_progs_no_alu32_parallel on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-22 success Logs for test_progs_parallel on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-23 success Logs for test_progs_parallel on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-24 success Logs for test_progs_parallel on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-27 success Logs for test_verifier on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-28 success Logs for test_verifier on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-29 success Logs for veristat
bpf/vmtest-bpf-VM_Test-26 success Logs for test_verifier on s390x with gcc
bpf/vmtest-bpf-VM_Test-16 fail Logs for test_progs_no_alu32 on s390x with gcc
bpf/vmtest-bpf-VM_Test-12 success Logs for test_progs on s390x with gcc
bpf/vmtest-bpf-VM_Test-8 success Logs for test_maps on s390x with gcc

Commit Message

Maxim Mikityanskiy June 7, 2023, 12:39 p.m. UTC 
From: Maxim Mikityanskiy <maxim@isovalent.com>

The previous commit fixed a verifier bypass by ensuring that ID is not
preserved on narrowing spills. Add the test cases to check the
problematic patterns.

Signed-off-by: Maxim Mikityanskiy <maxim@isovalent.com>
---
 .../selftests/bpf/progs/verifier_spill_fill.c | 79 +++++++++++++++++++
 1 file changed, 79 insertions(+)

Comments

Yonghong Song June 7, 2023, 3:35 p.m. UTC | #1 
On 6/7/23 5:39 AM, Maxim Mikityanskiy wrote:
> From: Maxim Mikityanskiy <maxim@isovalent.com>
> 
> The previous commit fixed a verifier bypass by ensuring that ID is not
> preserved on narrowing spills. Add the test cases to check the
> problematic patterns.
> 
> Signed-off-by: Maxim Mikityanskiy <maxim@isovalent.com>

Acked-by: Yonghong Song <yhs@fb.com>
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
index 136e5530b72c..6115520154e3 100644
--- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
+++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
@@ -371,4 +371,83 @@  __naked void and_then_at_fp_8(void)
 "	::: __clobber_all);
 }
 
+SEC("xdp")
+__description("32-bit spill of 64-bit reg should clear ID")
+__failure __msg("math between ctx pointer and 4294967295 is not allowed")
+__naked void spill_32bit_of_64bit_fail(void)
+{
+	asm volatile ("					\
+	r6 = r1;					\
+	/* Roll one bit to force the verifier to track both branches. */\
+	call %[bpf_get_prandom_u32];			\
+	r0 &= 0x8;					\
+	/* Put a large number into r1. */		\
+	r1 = 0xffffffff;				\
+	r1 <<= 32;					\
+	r1 += r0;					\
+	/* Assign an ID to r1. */			\
+	r2 = r1;					\
+	/* 32-bit spill r1 to stack - should clear the ID! */\
+	*(u32*)(r10 - 8) = r1;				\
+	/* 32-bit fill r2 from stack. */		\
+	r2 = *(u32*)(r10 - 8);				\
+	/* Compare r2 with another register to trigger find_equal_scalars.\
+	 * Having one random bit is important here, otherwise the verifier cuts\
+	 * the corners. If the ID was mistakenly preserved on spill, this would\
+	 * cause the verifier to think that r1 is also equal to zero in one of\
+	 * the branches, and equal to eight on the other branch.\
+	 */						\
+	r3 = 0;						\
+	if r2 != r3 goto l0_%=;				\
+l0_%=:	r1 >>= 32;					\
+	/* At this point, if the verifier thinks that r1 is 0, an out-of-bounds\
+	 * read will happen, because it actually contains 0xffffffff.\
+	 */						\
+	r6 += r1;					\
+	r0 = *(u32*)(r6 + 0);				\
+	exit;						\
+"	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
+SEC("xdp")
+__description("16-bit spill of 32-bit reg should clear ID")
+__failure __msg("dereference of modified ctx ptr R6 off=65535 disallowed")
+__naked void spill_16bit_of_32bit_fail(void)
+{
+	asm volatile ("					\
+	r6 = r1;					\
+	/* Roll one bit to force the verifier to track both branches. */\
+	call %[bpf_get_prandom_u32];			\
+	r0 &= 0x8;					\
+	/* Put a large number into r1. */		\
+	w1 = 0xffff0000;				\
+	r1 += r0;					\
+	/* Assign an ID to r1. */			\
+	r2 = r1;					\
+	/* 16-bit spill r1 to stack - should clear the ID! */\
+	*(u16*)(r10 - 8) = r1;				\
+	/* 16-bit fill r2 from stack. */		\
+	r2 = *(u16*)(r10 - 8);				\
+	/* Compare r2 with another register to trigger find_equal_scalars.\
+	 * Having one random bit is important here, otherwise the verifier cuts\
+	 * the corners. If the ID was mistakenly preserved on spill, this would\
+	 * cause the verifier to think that r1 is also equal to zero in one of\
+	 * the branches, and equal to eight on the other branch.\
+	 */						\
+	r3 = 0;						\
+	if r2 != r3 goto l0_%=;				\
+l0_%=:	r1 >>= 16;					\
+	/* At this point, if the verifier thinks that r1 is 0, an out-of-bounds\
+	 * read will happen, because it actually contains 0xffff.\
+	 */						\
+	r6 += r1;					\
+	r0 = *(u32*)(r6 + 0);				\
+	exit;						\
+"	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";