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

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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: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260408191242.526279-4-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann 2026-04-08 21:12:42 +02:00 committed by Alexei Starovoitov
parent 9dba0ae973
commit e0fcb42bc6
1 changed files with 142 additions and 0 deletions
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142
tools/testing/selftests/bpf/progs/verifier_ld_ind.c
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@ -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";