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selftests/bpf: Reject legacy packet loads from callbacks

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Add verifier coverage for the callback restriction on legacy packet
loads. Exercise BPF_LD_ABS directly in a bpf_loop callback and
BPF_LD_IND from a static subprogram called by the callback, ensuring that
callback context follows nested static calls.

Also exercise a callback which reaches BPF_LD_IND through a global
function and its static descendant. A sibling success case calls the same
global chain outside a callback, preserving support for ordinary global
packet loads. Existing success cases continue to cover loads from ordinary
static subprograms.

The failure cases expect the policy-specific rejection instead of reaching
the implicit-return path, triggering a verifier warning, or being accepted
through a function boundary.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260903214758.2727663-9-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi
2026-09-03 23:47:54 +02:00
committed by Alexei Starovoitov
parent e7d28823c6
commit 23724e009f
1 changed files with 96 additions and 0 deletions
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96
tools/testing/selftests/bpf/progs/verifier_ld_ind.c
View File

@@ -194,6 +194,102 @@ __naked void ld_ind_subprog_both_paths_safe(void)
::: __clobber_all);
}
__naked __noinline __used
static int ld_abs_callback(void)
{
asm volatile (
"r6 = *(u64 *)(r2 + 0);"
".8byte %[ld_abs];"
"r0 = 0;"
"exit;"
:
: __imm_insn(ld_abs, BPF_LD_ABS(BPF_W, 0))
: __clobber_all);
}
SEC("socket")
__description("ld_abs: reject in callback")
__failure __msg("cannot use BPF_LD_[ABS|IND] within callback")
int ld_abs_callback_reject(struct __sk_buff *skb)
{
bpf_loop(1, ld_abs_callback, &skb, 0);
return 0;
}
__naked __noinline __used
static int ld_ind_callback_subprog(void)
{
asm volatile (
"r6 = r1;"
"r7 = 0;"
".8byte %[ld_ind];"
"r0 = 0;"
"exit;"
:
: __imm_insn(ld_ind, BPF_LD_IND(BPF_W, BPF_REG_7, 0))
: __clobber_all);
}
__naked __noinline __used
static int ld_ind_callback(void)
{
asm volatile (
"r1 = *(u64 *)(r2 + 0);"
"call ld_ind_callback_subprog;"
"exit;"
::: __clobber_all);
}
SEC("socket")
__description("ld_ind: reject in callback subprog")
__failure __msg("cannot use BPF_LD_[ABS|IND] within callback")
int ld_ind_callback_subprog_reject(struct __sk_buff *skb)
{
bpf_loop(1, ld_ind_callback, &skb, 0);
return 0;
}
static __noinline int ld_ind_global_static(struct __sk_buff *skb)
{
asm volatile (
"r6 = %[skb];"
"r7 = 0;"
".8byte %[ld_ind];"
:
: [skb] "r"(skb),
__imm_insn(ld_ind, BPF_LD_IND(BPF_W, BPF_REG_7, 0))
: __clobber_common, "r6", "r7");
return skb->mark;
}
__noinline int ld_ind_global(struct __sk_buff *skb)
{
return ld_ind_global_static(skb);
}
static int ld_ind_global_callback(__u32 index, struct __sk_buff **ctx)
{
ld_ind_global(*ctx);
return 0;
}
SEC("socket")
__description("ld_ind: reject in callback global subprog")
__failure __msg("cannot use BPF_LD_[ABS|IND] within callback")
int ld_ind_global_callback_reject(struct __sk_buff *skb)
{
bpf_loop(1, ld_ind_global_callback, &skb, 0);
return 0;
}
SEC("socket")
__description("ld_ind: allow in non-callback global subprog")
__success
int ld_ind_global_subprog_ok(struct __sk_buff *skb)
{
return ld_ind_global(skb);
}
/*
* ld_{abs,ind} in subprogs require scalar (int) return type in BTF.
* A test with void return must be rejected.