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bpf: Distinguish function references in policy diagnostics

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add_subprogs() rejects both BPF-to-BPF calls and BPF_PSEUDO_FUNC loads for
unprivileged programs. The latter loads a subprogram address for use as a
callback, but its Policy report currently describes it as a function call and
suggests avoiding calls that the program does not contain.

Select the operation and suggestion from the instruction kind. Preserve the
existing call wording for BPF_PSEUDO_CALL, and describe BPF_PSEUDO_FUNC as a
BPF function reference.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/bpf/d02e6a6d3b2dc43a207b8ba836ce62497b250dede9252e7409c5212201c794b7@mail.kernel.org
Link: https://lore.kernel.org/bpf/20260816015746.2632990-14-memxor@gmail.com
This commit is contained in:
Kumar Kartikeya Dwivedi
2026-08-16 03:57:41 +02:00
parent 6bd520a6e3
commit fc009f4658
1 changed files with 10 additions and 2 deletions
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12
kernel/bpf/verifier.c
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@@ -2912,6 +2912,7 @@ static int add_subprogs(struct bpf_verifier_env *env)
struct bpf_subprog_info *subprog = env->subprog_info;
int i, ret, insn_cnt = env->prog->len, ex_cb_insn;
struct bpf_insn *insn = env->prog->insnsi;
const char *operation, *suggestion;
/* Add entry function. */
ret = add_subprog(env, 0);
@@ -2923,11 +2924,18 @@ static int add_subprogs(struct bpf_verifier_env *env)
continue;
if (!env->bpf_capable) {
if (bpf_pseudo_func(insn)) {
operation = "BPF function reference";
suggestion = "Load this program with the required capability, or avoid BPF function references in unprivileged programs.";
} else {
operation = "BPF-to-BPF function call";
suggestion = "Load this program with the required capability, or avoid BPF-to-BPF function calls in unprivileged programs.";
}
verbose(env, "loading/calling other bpf or kernel functions are allowed for CAP_BPF and CAP_SYS_ADMIN\n");
bpf_diag_policy(
env, i, "BPF-to-BPF function call",
env, i, operation,
"loading or calling other BPF functions requires CAP_BPF or CAP_SYS_ADMIN",
"Load this program with the required capability, or avoid BPF-to-BPF function calls in unprivileged programs.");
suggestion);
return -EPERM;
}