Re: [PATCH bpf-next 2/3] bpf: Add a BPF helper for getting the IMA hash of an inode
From: Alexei Starovoitov <hidden>
Date: 2020-11-24 04:02:34
Also in:
bpf, lkml
On Fri, Nov 20, 2020 at 01:17:07PM +0000, KP Singh wrote:
quoted hunk ↗ jump to hunk
+ +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.