Commit e0fcb42b authored by Daniel Borkmann's avatar Daniel Borkmann Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add tests for ld_{abs,ind} failure path in subprogs 



Extend the verifier_ld_ind BPF selftests with subprogs containing
ld_{abs,ind} and craft the test in a way where the invalid register
read is rejected in the fixed case. Also add a success case each,
and add additional coverage related to the BTF return type enforcement.

  # LDLIBS=-static PKG_CONFIG='pkg-config --static' ./vmtest.sh -- ./test_progs -t verifier_ld_ind
  [...]
  #611/1   verifier_ld_ind/ld_ind: check calling conv, r1:OK
  #611/2   verifier_ld_ind/ld_ind: check calling conv, r1 @unpriv:OK
  #611/3   verifier_ld_ind/ld_ind: check calling conv, r2:OK
  #611/4   verifier_ld_ind/ld_ind: check calling conv, r2 @unpriv:OK
  #611/5   verifier_ld_ind/ld_ind: check calling conv, r3:OK
  #611/6   verifier_ld_ind/ld_ind: check calling conv, r3 @unpriv:OK
  #611/7   verifier_ld_ind/ld_ind: check calling conv, r4:OK
  #611/8   verifier_ld_ind/ld_ind: check calling conv, r4 @unpriv:OK
  #611/9   verifier_ld_ind/ld_ind: check calling conv, r5:OK
  #611/10  verifier_ld_ind/ld_ind: check calling conv, r5 @unpriv:OK
  #611/11  verifier_ld_ind/ld_ind: check calling conv, r7:OK
  #611/12  verifier_ld_ind/ld_ind: check calling conv, r7 @unpriv:OK
  #611/13  verifier_ld_ind/ld_abs: subprog early exit on ld_abs failure:OK
  #611/14  verifier_ld_ind/ld_ind: subprog early exit on ld_ind failure:OK
  #611/15  verifier_ld_ind/ld_abs: subprog with both paths safe:OK
  #611/16  verifier_ld_ind/ld_ind: subprog with both paths safe:OK
  #611/17  verifier_ld_ind/ld_abs: reject void return subprog:OK
  #611/18  verifier_ld_ind/ld_ind: reject void return subprog:OK
  #611     verifier_ld_ind:OK
  Summary: 1/18 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260408191242.526279-4-daniel@iogearbox.net


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 9dba0ae9

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

+142 −0
Original line number Diff line number Diff line
@@ -107,4 +107,146 @@ __naked void ind_check_calling_conv_r7(void) 
	: __clobber_all);

}



/*

 * ld_{abs,ind} subprog that always sets r0=1 on the success path.

 * bpf_gen_ld_abs() emits a hidden exit with r0=0 when the load helper

 * fails. The verifier must model this failure return so that callers

 * account for r0=0 as a possible return value.

 */

__naked __noinline __used

static int ldabs_subprog(void)

{

	asm volatile (

	"r6 = r1;"

	".8byte %[ld_abs];"

	"r0 = 1;"

	"exit;"

	:

	: __imm_insn(ld_abs, BPF_LD_ABS(BPF_W, 0))

	: __clobber_all);

}



__naked __noinline __used

static int ldind_subprog(void)

{

	asm volatile (

	"r6 = r1;"

	"r7 = 0;"

	".8byte %[ld_ind];"

	"r0 = 1;"

	"exit;"

	:

	: __imm_insn(ld_ind, BPF_LD_IND(BPF_W, BPF_REG_7, 0))

	: __clobber_all);

}



SEC("socket")

__description("ld_abs: subprog early exit on ld_abs failure")

__failure __msg("R9 !read_ok")

__naked void ld_abs_subprog_early_exit(void)

{

	asm volatile (

	"call ldabs_subprog;"

	"if r0 != 0 goto l_exit_%=;"

	"r0 = r9;"

	"l_exit_%=:"

	"r0 = 0;"

	"exit;"

	::: __clobber_all);

}



SEC("socket")

__description("ld_ind: subprog early exit on ld_ind failure")

__failure __msg("R9 !read_ok")

__naked void ld_ind_subprog_early_exit(void)

{

	asm volatile (

	"call ldind_subprog;"

	"if r0 != 0 goto l_exit_%=;"

	"r0 = r9;"

	"l_exit_%=:"

	"r0 = 0;"

	"exit;"

	::: __clobber_all);

}



SEC("socket")

__description("ld_abs: subprog with both paths safe")

__success

__naked void ld_abs_subprog_both_paths_safe(void)

{

	asm volatile (

	"call ldabs_subprog;"

	"r0 = 0;"

	"exit;"

	::: __clobber_all);

}



SEC("socket")

__description("ld_ind: subprog with both paths safe")

__success

__naked void ld_ind_subprog_both_paths_safe(void)

{

	asm volatile (

	"call ldind_subprog;"

	"r0 = 0;"

	"exit;"

	::: __clobber_all);

}



/*

 * ld_{abs,ind} in subprogs require scalar (int) return type in BTF.

 * A test with void return must be rejected.

 */

__naked __noinline __used

static void ldabs_void_subprog(void)

{

	asm volatile (

	"r6 = r1;"

	".8byte %[ld_abs];"

	"r0 = 1;"

	"exit;"

	:

	: __imm_insn(ld_abs, BPF_LD_ABS(BPF_W, 0))

	: __clobber_all);

}



SEC("socket")

__description("ld_abs: reject void return subprog")

__failure __msg("LD_ABS is only allowed in functions that return 'int'")

__naked void ld_abs_void_subprog_reject(void)

{

	asm volatile (

	"call ldabs_void_subprog;"

	"r0 = 0;"

	"exit;"

	::: __clobber_all);

}



__naked __noinline __used

static void ldind_void_subprog(void)

{

	asm volatile (

	"r6 = r1;"

	"r7 = 0;"

	".8byte %[ld_ind];"

	"r0 = 1;"

	"exit;"

	:

	: __imm_insn(ld_ind, BPF_LD_IND(BPF_W, BPF_REG_7, 0))

	: __clobber_all);

}



SEC("socket")

__description("ld_ind: reject void return subprog")

__failure __msg("LD_ABS is only allowed in functions that return 'int'")

__naked void ld_ind_void_subprog_reject(void)

{

	asm volatile (

	"call ldind_void_subprog;"

	"r0 = 0;"

	"exit;"

	::: __clobber_all);

}



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