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Mon, 23 Nov 2020 20:02:22 -0800 (PST) Date: Mon, 23 Nov 2020 20:02:20 -0800 From: Alexei Starovoitov To: KP Singh Cc: James Morris , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-security-module@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Florent Revest , Brendan Jackman , Mimi Zohar Subject: Re: [PATCH bpf-next 2/3] bpf: Add a BPF helper for getting the IMA hash of an inode Message-ID: <20201124040220.oyajc7wqn7gqgyib@ast-mbp> References: <20201120131708.3237864-1-kpsingh@chromium.org> <20201120131708.3237864-2-kpsingh@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201120131708.3237864-2-kpsingh@chromium.org> Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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. "lsm/" is non-sleepable. "lsm.s/" is. please enable CONFIG_DEBUG_ATOMIC_SLEEP=y in your config.