[PATCH bpf-next v8 2/4] bpf: Introduce might_sleep field in bpf_func_proto

[Yonghong Song <yhs@fb.com>]

Introduce bpf_func_proto->might_sleep to indicate a particular helper
might sleep. This will make later check whether a helper might be
sleepable or not easier.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 include/linux/bpf.h      | 1 +
 kernel/bpf/bpf_lsm.c     | 6 ++++--
 kernel/bpf/helpers.c     | 2 ++
 kernel/bpf/verifier.c    | 5 +++++
 kernel/trace/bpf_trace.c | 4 ++--
 5 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c9eafa67f2a2..43fd7eeeeabb 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -682,6 +682,7 @@ struct bpf_func_proto {
 	u64 (*func)(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 	bool gpl_only;
 	bool pkt_access;
+	bool might_sleep;
 	enum bpf_return_type ret_type;
 	union {
 		struct {
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index d6c9b3705f24..ae0267f150b5 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -151,6 +151,7 @@ BTF_ID_LIST_SINGLE(bpf_ima_inode_hash_btf_ids, struct, inode)
 static const struct bpf_func_proto bpf_ima_inode_hash_proto = {
 	.func		= bpf_ima_inode_hash,
 	.gpl_only	= false,
+	.might_sleep	= true,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_BTF_ID,
 	.arg1_btf_id	= &bpf_ima_inode_hash_btf_ids[0],
@@ -169,6 +170,7 @@ BTF_ID_LIST_SINGLE(bpf_ima_file_hash_btf_ids, struct, file)
 static const struct bpf_func_proto bpf_ima_file_hash_proto = {
 	.func		= bpf_ima_file_hash,
 	.gpl_only	= false,
+	.might_sleep	= true,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_BTF_ID,
 	.arg1_btf_id	= &bpf_ima_file_hash_btf_ids[0],
@@ -221,9 +223,9 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_bprm_opts_set:
 		return &bpf_bprm_opts_set_proto;
 	case BPF_FUNC_ima_inode_hash:
-		return prog->aux->sleepable ? &bpf_ima_inode_hash_proto : NULL;
+		return &bpf_ima_inode_hash_proto;
 	case BPF_FUNC_ima_file_hash:
-		return prog->aux->sleepable ? &bpf_ima_file_hash_proto : NULL;
+		return &bpf_ima_file_hash_proto;
 	case BPF_FUNC_get_attach_cookie:
 		return bpf_prog_has_trampoline(prog) ? &bpf_get_attach_cookie_proto : NULL;
 #ifdef CONFIG_NET
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 9e8a5557ea8d..c3b798a1e3e9 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -660,6 +660,7 @@ BPF_CALL_3(bpf_copy_from_user, void *, dst, u32, size,
 const struct bpf_func_proto bpf_copy_from_user_proto = {
 	.func		= bpf_copy_from_user,
 	.gpl_only	= false,
+	.might_sleep	= true,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_UNINIT_MEM,
 	.arg2_type	= ARG_CONST_SIZE_OR_ZERO,
@@ -690,6 +691,7 @@ BPF_CALL_5(bpf_copy_from_user_task, void *, dst, u32, size,
 const struct bpf_func_proto bpf_copy_from_user_task_proto = {
 	.func		= bpf_copy_from_user_task,
 	.gpl_only	= true,
+	.might_sleep	= true,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_UNINIT_MEM,
 	.arg2_type	= ARG_CONST_SIZE_OR_ZERO,
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9528a066cfa5..068cc885903c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7516,6 +7516,11 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 		return -EINVAL;
 	}
 
+	if (!env->prog->aux->sleepable && fn->might_sleep) {
+		verbose(env, "helper call might sleep in a non-sleepable prog\n");
+		return -EINVAL;
+	}
+
 	/* With LD_ABS/IND some JITs save/restore skb from r1. */
 	changes_data = bpf_helper_changes_pkt_data(fn->func);
 	if (changes_data && fn->arg1_type != ARG_PTR_TO_CTX) {
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 5b9008bc597b..3bbd3f0c810c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1485,9 +1485,9 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_get_task_stack:
 		return &bpf_get_task_stack_proto;
 	case BPF_FUNC_copy_from_user:
-		return prog->aux->sleepable ? &bpf_copy_from_user_proto : NULL;
+		return &bpf_copy_from_user_proto;
 	case BPF_FUNC_copy_from_user_task:
-		return prog->aux->sleepable ? &bpf_copy_from_user_task_proto : NULL;
+		return &bpf_copy_from_user_task_proto;
 	case BPF_FUNC_snprintf_btf:
 		return &bpf_snprintf_btf_proto;
 	case BPF_FUNC_per_cpu_ptr:
-- 
2.30.2