Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge branch 'bpf-allow-access-to-const-void-pointer-arguments-in-tracing-programs'
KaFai Wan says:
====================
bpf: Allow access to const void pointer arguments in tracing programs
If we try to access argument which is pointer to const void, it's an
UNKNOWN type, verifier will fail to load.
Use is_void_or_int_ptr to check if type is void or int pointer.
Add a selftest to check it.
---
====================
Link: https://patch.msgid.link/20250423121329.3163461-1-mannkafai@gmail.com
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
+26
-12
+7
-11
kernel/bpf/btf.c
+7
-11
kernel/bpf/btf.c
···
6383
6383
return prog->aux->attach_btf;
6384
6384
}
6385
6385
6386
-
static bool is_int_ptr(struct btf *btf, const struct btf_type *t)
6386
+
static bool is_void_or_int_ptr(struct btf *btf, const struct btf_type *t)
6387
6387
{
6388
6388
/* skip modifiers */
6389
6389
t = btf_type_skip_modifiers(btf, t->type, NULL);
6390
-
6391
-
return btf_type_is_int(t);
6390
+
return btf_type_is_void(t) || btf_type_is_int(t);
6392
6391
}
6393
6392
6394
6393
static u32 get_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto,
···
6775
6776
}
6776
6777
}
6777
6778
6778
-
if (t->type == 0)
6779
-
/* This is a pointer to void.
6780
-
* It is the same as scalar from the verifier safety pov.
6781
-
* No further pointer walking is allowed.
6782
-
*/
6783
-
return true;
6784
-
6785
-
if (is_int_ptr(btf, t))
6779
+
/*
6780
+
* If it's a pointer to void, it's the same as scalar from the verifier
6781
+
* safety POV. Either way, no futher pointer walking is allowed.
6782
+
*/
6783
+
if (is_void_or_int_ptr(btf, t))
6786
6784
return true;
6787
6785
6788
6786
/* this is a pointer to another type */
+7
-1
net/bpf/test_run.c
+7
-1
net/bpf/test_run.c
···
569
569
return *a;
570
570
}
571
571
572
+
int noinline bpf_fentry_test10(const void *a)
573
+
{
574
+
return (long)a;
575
+
}
576
+
572
577
void noinline bpf_fentry_test_sinfo(struct skb_shared_info *sinfo)
573
578
{
574
579
}
···
704
699
bpf_fentry_test6(16, (void *)17, 18, 19, (void *)20, 21) != 111 ||
705
700
bpf_fentry_test7((struct bpf_fentry_test_t *)0) != 0 ||
706
701
bpf_fentry_test8(&arg) != 0 ||
707
-
bpf_fentry_test9(&retval) != 0)
702
+
bpf_fentry_test9(&retval) != 0 ||
703
+
bpf_fentry_test10((void *)0) != 0)
708
704
goto out;
709
705
break;
710
706
case BPF_MODIFY_RETURN:
+12
tools/testing/selftests/bpf/progs/verifier_btf_ctx_access.c
+12
tools/testing/selftests/bpf/progs/verifier_btf_ctx_access.c
···
65
65
" ::: __clobber_all);
66
66
}
67
67
68
+
SEC("fentry/bpf_fentry_test10")
69
+
__description("btf_ctx_access const void pointer accept")
70
+
__success __retval(0)
71
+
__naked void ctx_access_const_void_pointer_accept(void)
72
+
{
73
+
asm volatile (" \
74
+
r2 = *(u64 *)(r1 + 0); /* load 1st argument value (const void pointer) */\
75
+
r0 = 0; \
76
+
exit; \
77
+
" ::: __clobber_all);
78
+
}
79
+
68
80
char _license[] SEC("license") = "GPL";