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bpf: Reject stack arguments if tail call reachable

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Tail calls are deprecated and will be replaced by indirect calls
in the future. Reject programs that combine tail calls with stack
arguments rather than adding complexity for a deprecated feature.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260513045109.2392108-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Yonghong Song 2026-05-12 21:51:09 -07:00 committed by Alexei Starovoitov
parent e0b7b91c72
commit 35b7873316
1 changed files with 10 additions and 1 deletions
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11
kernel/bpf/verifier.c
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@ -5267,14 +5267,23 @@ static int check_max_stack_depth_subprog(struct bpf_verifier_env *env, int idx,
* this info will be utilized by JIT so that we will be preserving the
* tail call counter throughout bpf2bpf calls combined with tailcalls
*/
if (tail_call_reachable)
if (tail_call_reachable) {
for (tmp = idx; tmp >= 0; tmp = dinfo[tmp].caller) {
if (subprog[tmp].is_exception_cb) {
verbose(env, "cannot tail call within exception cb\n");
return -EINVAL;
}
if (subprog[tmp].stack_arg_cnt) {
verbose(env, "tail_calls are not allowed in programs with stack args\n");
return -EINVAL;
}
subprog[tmp].tail_call_reachable = true;
}
} else if (!idx && subprog[0].has_tail_call && subprog[0].stack_arg_cnt) {
verbose(env, "tail_calls are not allowed in programs with stack args\n");
return -EINVAL;
}
if (subprog[0].tail_call_reachable)
env->prog->aux->tail_call_reachable = true;