Commit 0ad1734c authored by Daniel Wade's avatar Daniel Wade Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add tests for maybe_fork_scalars() OR vs AND handling 



Add three test cases to verifier_bounds.c to verify that
maybe_fork_scalars() correctly tracks register values for BPF_OR
operations with constant source operands:

1. or_scalar_fork_rejects_oob: After ARSH 63 + OR 8, the pushed
   path should have dst = 8. With value_size = 8, accessing
   map_value + 8 is out of bounds and must be rejected.

2. and_scalar_fork_still_works: Regression test ensuring AND
   forking continues to work. ARSH 63 + AND 4 produces pushed
   dst = 0 and current dst = 4, both within value_size = 8.

3. or_scalar_fork_allows_inbounds: After ARSH 63 + OR 4, the
   pushed path has dst = 4, which is within value_size = 8
   and should be accepted.

These tests exercise the fix in the previous patch, which makes the
pushed path re-execute the ALU instruction so it computes the correct
result for BPF_OR.

Signed-off-by: default avatarDaniel Wade <danjwade95@gmail.com>
Reviewed-by: default avatarAmery Hung <ameryhung@gmail.com>
Acked-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260314021521.128361-3-danjwade95@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent c845894e

tools/testing/selftests/bpf/progs/verifier_bounds.c

+94 −0
Original line number Diff line number Diff line
@@ -2037,4 +2037,98 @@ __naked void signed_unsigned_intersection32_case2(void *ctx) 
	: __clobber_all);

}



SEC("socket")

__description("maybe_fork_scalars: OR with constant rejects OOB")

__failure __msg("invalid access to map value")

__naked void or_scalar_fork_rejects_oob(void)

{

	asm volatile ("					\

	r1 = 0;						\

	*(u64*)(r10 - 8) = r1;				\

	r2 = r10;					\

	r2 += -8;					\

	r1 = %[map_hash_8b] ll;				\

	call %[bpf_map_lookup_elem];			\

	if r0 == 0 goto l0_%=;				\

	r9 = r0;					\

	r6 = *(u64*)(r9 + 0);				\

	r6 s>>= 63;					\

	r6 |= 8;					\

	/* r6 is -1 (current) or 8 (pushed) */		\

	if r6 s< 0 goto l0_%=;				\

	/* pushed path: r6 = 8, OOB for value_size=8 */	\

	r9 += r6;					\

	r0 = *(u8*)(r9 + 0);				\

l0_%=:	r0 = 0;						\

	exit;						\

"	:

	: __imm(bpf_map_lookup_elem),

	  __imm_addr(map_hash_8b)

	: __clobber_all);

}



SEC("socket")

__description("maybe_fork_scalars: AND with constant still works")

__success __retval(0)

__naked void and_scalar_fork_still_works(void)

{

	asm volatile ("					\

	r1 = 0;						\

	*(u64*)(r10 - 8) = r1;				\

	r2 = r10;					\

	r2 += -8;					\

	r1 = %[map_hash_8b] ll;				\

	call %[bpf_map_lookup_elem];			\

	if r0 == 0 goto l0_%=;				\

	r9 = r0;					\

	r6 = *(u64*)(r9 + 0);				\

	r6 s>>= 63;					\

	r6 &= 4;					\

	/*						\

	 * r6 is 0 (pushed, 0&4==0) or 4 (current)	\

	 * both within value_size=8			\

	 */						\

	if r6 s< 0 goto l0_%=;				\

	r9 += r6;					\

	r0 = *(u8*)(r9 + 0);				\

l0_%=:	r0 = 0;						\

	exit;						\

"	:

	: __imm(bpf_map_lookup_elem),

	  __imm_addr(map_hash_8b)

	: __clobber_all);

}



SEC("socket")

__description("maybe_fork_scalars: OR with constant allows in-bounds")

__success __retval(0)

__naked void or_scalar_fork_allows_inbounds(void)

{

	asm volatile ("					\

	r1 = 0;						\

	*(u64*)(r10 - 8) = r1;				\

	r2 = r10;					\

	r2 += -8;					\

	r1 = %[map_hash_8b] ll;				\

	call %[bpf_map_lookup_elem];			\

	if r0 == 0 goto l0_%=;				\

	r9 = r0;					\

	r6 = *(u64*)(r9 + 0);				\

	r6 s>>= 63;					\

	r6 |= 4;					\

	/*						\

	 * r6 is -1 (current) or 4 (pushed)		\

	 * pushed path: r6 = 4, within value_size=8	\

	 */						\

	if r6 s< 0 goto l0_%=;				\

	r9 += r6;					\

	r0 = *(u8*)(r9 + 0);				\

l0_%=:	r0 = 0;						\

	exit;						\

"	:

	: __imm(bpf_map_lookup_elem),

	  __imm_addr(map_hash_8b)

	: __clobber_all);

}



char _license[] SEC("license") = "GPL";