On Tue, Nov 24, 2020 at 5:02 AM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> On Fri, Nov 20, 2020 at 01:17:07PM +0000, KP Singh wrote:
> > +
> > +static bool bpf_ima_inode_hash_allowed(const struct bpf_prog *prog)
> > +{
> > + return bpf_lsm_is_sleepable_hook(prog->aux->attach_btf_id);
> > +}
> > +
> > +BTF_ID_LIST_SINGLE(bpf_ima_inode_hash_btf_ids, struct, inode)
> > +
> > +const static struct bpf_func_proto bpf_ima_inode_hash_proto = {
> > + .func = bpf_ima_inode_hash,
> > + .gpl_only = false,
> > + .ret_type = RET_INTEGER,
> > + .arg1_type = ARG_PTR_TO_BTF_ID,
> > + .arg1_btf_id = &bpf_ima_inode_hash_btf_ids[0],
> > + .arg2_type = ARG_PTR_TO_UNINIT_MEM,
> > + .arg3_type = ARG_CONST_SIZE_OR_ZERO,
> > + .allowed = bpf_ima_inode_hash_allowed,
> > +};
> > +
> > static const struct bpf_func_proto *
> > bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> > {
> > @@ -97,6 +121,8 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> > return &bpf_task_storage_delete_proto;
> > case BPF_FUNC_bprm_opts_set:
> > return &bpf_bprm_opts_set_proto;
> > + case BPF_FUNC_ima_inode_hash:
> > + return &bpf_ima_inode_hash_proto;
>
> That's not enough for correctness.
> Not only hook has to sleepable, but the program has to be sleepable too.
> The patch 3 should be causing all sort of kernel warnings
> for calling mutex from preempt disabled.
> There it calls bpf_ima_inode_hash() from SEC("lsm/file_mprotect") program.
I did actually mean to use SEC("lsm.s/bprm_committed_creds"), my bad.
> "lsm/" is non-sleepable. "lsm.s/" is.
> please enable CONFIG_DEBUG_ATOMIC_SLEEP=y in your config.
Oops, yes I did notice that during recent work on the test cases.
Since we need a stronger check than just warnings, I am doing
something similar to
what we do for bpf_copy_from_user i.e.
return prog->aux->sleepable ? &bpf_ima_inode_hash_proto : NULL;
