bpf: Replace RET_XXX_OR_NULL with RET_XXX | PTR_MAYBE_NULL

mainline inclusion
from mainline-v5.17-rc1
commit 3c480732
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4WRPV
CVE: CVE-2022-0500

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3c4807322660d4290ac9062c034aed6b87243861

--------------------------------

We have introduced a new type to make bpf_ret composable, by
reserving high bits to represent flags.

One of the flag is PTR_MAYBE_NULL, which indicates a pointer
may be NULL. When applying this flag to ret_types, it means
the returned value could be a NULL pointer. This patch
switches the qualified arg_types to use this flag.
The ret_types changed in this patch include:

1. RET_PTR_TO_MAP_VALUE_OR_NULL
2. RET_PTR_TO_SOCKET_OR_NULL
3. RET_PTR_TO_TCP_SOCK_OR_NULL
4. RET_PTR_TO_SOCK_COMMON_OR_NULL
5. RET_PTR_TO_ALLOC_MEM_OR_NULL
6. RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL
7. RET_PTR_TO_BTF_ID_OR_NULL

This patch doesn't eliminate the use of these names, instead
it makes them aliases to 'RET_PTR_TO_XXX | PTR_MAYBE_NULL'.
Signed-off-by: NHao Luo <haoluo@google.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-4-haoluo@google.com
Conflicts:
	kernel/bpf/verifier.c
Signed-off-by: NPu Lehui <pulehui@huawei.com>
Reviewed-by: NKuohai Xu <xukuohai@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

include/linux/bpf.h

@@ -334,16 +334,22 @@ enum bpf_return_type {
 	RET_INTEGER,			/* function returns integer */
 	RET_VOID,			/* function doesn't return anything */
 	RET_PTR_TO_MAP_VALUE,		/* returns a pointer to map elem value */
-	RET_PTR_TO_MAP_VALUE_OR_NULL,	/* returns a pointer to map elem value or NULL */
-	RET_PTR_TO_SOCKET_OR_NULL,	/* returns a pointer to a socket or NULL */
-	RET_PTR_TO_TCP_SOCK_OR_NULL,	/* returns a pointer to a tcp_sock or NULL */
-	RET_PTR_TO_SOCK_COMMON_OR_NULL,	/* returns a pointer to a sock_common or NULL */
-	RET_PTR_TO_ALLOC_MEM_OR_NULL,	/* returns a pointer to dynamically allocated memory or NULL */
-	RET_PTR_TO_BTF_ID_OR_NULL,	/* returns a pointer to a btf_id or NULL */
-	RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL, /* returns a pointer to a valid memory or a btf_id or NULL */
+	RET_PTR_TO_SOCKET,		/* returns a pointer to a socket */
+	RET_PTR_TO_TCP_SOCK,		/* returns a pointer to a tcp_sock */
+	RET_PTR_TO_SOCK_COMMON,		/* returns a pointer to a sock_common */
+	RET_PTR_TO_ALLOC_MEM,		/* returns a pointer to dynamically allocated memory */
 	RET_PTR_TO_MEM_OR_BTF_ID,	/* returns a pointer to a valid memory or a btf_id */
+	RET_PTR_TO_BTF_ID,		/* returns a pointer to a btf_id */
 	__BPF_RET_TYPE_MAX,
 
+	/* Extended ret_types. */
+	RET_PTR_TO_MAP_VALUE_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_MAP_VALUE,
+	RET_PTR_TO_SOCKET_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCKET,
+	RET_PTR_TO_TCP_SOCK_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_TCP_SOCK,
+	RET_PTR_TO_SOCK_COMMON_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCK_COMMON,
+	RET_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_ALLOC_MEM,
+	RET_PTR_TO_BTF_ID_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_BTF_ID,
+
 	/* This must be the last entry. Its purpose is to ensure the enum is
 	 * wide enough to hold the higher bits reserved for bpf_type_flag.
 	 */

kernel/bpf/helpers.c

@@ -636,7 +636,7 @@ BPF_CALL_2(bpf_per_cpu_ptr, const void *, ptr, u32, cpu)
 const struct bpf_func_proto bpf_per_cpu_ptr_proto = {
 	.func		= bpf_per_cpu_ptr,
 	.gpl_only	= false,
-	.ret_type	= RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL,
+	.ret_type	= RET_PTR_TO_MEM_OR_BTF_ID | PTR_MAYBE_NULL,
 	.arg1_type	= ARG_PTR_TO_PERCPU_BTF_ID,
 	.arg2_type	= ARG_ANYTHING,
 };

kernel/bpf/verifier.c

@@ -5322,6 +5322,7 @@ static int check_reference_leak(struct bpf_verifier_env *env)
 static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn_idx)
 {
 	const struct bpf_func_proto *fn = NULL;
+	enum bpf_return_type ret_type;
 	struct bpf_reg_state *regs;
 	struct bpf_call_arg_meta meta;
 	bool changes_data;
@@ -5433,13 +5434,13 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
 	regs[BPF_REG_0].subreg_def = DEF_NOT_SUBREG;
 
 	/* update return register (already marked as written above) */
-	if (fn->ret_type == RET_INTEGER) {
+	ret_type = fn->ret_type;
+	if (ret_type == RET_INTEGER) {
 		/* sets type to SCALAR_VALUE */
 		mark_reg_unknown(env, regs, BPF_REG_0);
-	} else if (fn->ret_type == RET_VOID) {
+	} else if (ret_type == RET_VOID) {
 		regs[BPF_REG_0].type = NOT_INIT;
-	} else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL ||
-		   fn->ret_type == RET_PTR_TO_MAP_VALUE) {
+	} else if (base_type(ret_type) == RET_PTR_TO_MAP_VALUE) {
 		/* There is no offset yet applied, variable or fixed */
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		/* remember map_ptr, so that check_map_access()
@@ -5452,28 +5453,27 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
 			return -EINVAL;
 		}
 		regs[BPF_REG_0].map_ptr = meta.map_ptr;
-		if (fn->ret_type == RET_PTR_TO_MAP_VALUE) {
+		if (type_may_be_null(ret_type)) {
+			regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
+		} else {
 			regs[BPF_REG_0].type = PTR_TO_MAP_VALUE;
 			if (map_value_has_spin_lock(meta.map_ptr))
 				regs[BPF_REG_0].id = ++env->id_gen;
-		} else {
-			regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
 		}
-	} else if (fn->ret_type == RET_PTR_TO_SOCKET_OR_NULL) {
+	} else if (base_type(ret_type) == RET_PTR_TO_SOCKET) {
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		regs[BPF_REG_0].type = PTR_TO_SOCKET_OR_NULL;
-	} else if (fn->ret_type == RET_PTR_TO_SOCK_COMMON_OR_NULL) {
+	} else if (base_type(ret_type) == RET_PTR_TO_SOCK_COMMON) {
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		regs[BPF_REG_0].type = PTR_TO_SOCK_COMMON_OR_NULL;
-	} else if (fn->ret_type == RET_PTR_TO_TCP_SOCK_OR_NULL) {
+	} else if (base_type(ret_type) == RET_PTR_TO_TCP_SOCK) {
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		regs[BPF_REG_0].type = PTR_TO_TCP_SOCK_OR_NULL;
-	} else if (fn->ret_type == RET_PTR_TO_ALLOC_MEM_OR_NULL) {
+	} else if (base_type(ret_type) == RET_PTR_TO_ALLOC_MEM) {
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		regs[BPF_REG_0].type = PTR_TO_MEM_OR_NULL;
 		regs[BPF_REG_0].mem_size = meta.mem_size;
-	} else if (fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL ||
-		   fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID) {
+	} else if (base_type(ret_type) == RET_PTR_TO_MEM_OR_BTF_ID) {
 		const struct btf_type *t;
 
 		mark_reg_known_zero(env, regs, BPF_REG_0);
@@ -5492,30 +5492,31 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
 				return -EINVAL;
 			}
 			regs[BPF_REG_0].type =
-				fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID ?
-				PTR_TO_MEM : PTR_TO_MEM_OR_NULL;
+				(ret_type & PTR_MAYBE_NULL) ?
+				PTR_TO_MEM_OR_NULL : PTR_TO_MEM;
 			regs[BPF_REG_0].mem_size = tsize;
 		} else {
 			regs[BPF_REG_0].type =
-				fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID ?
-				PTR_TO_BTF_ID : PTR_TO_BTF_ID_OR_NULL;
+				(ret_type & PTR_MAYBE_NULL) ?
+				PTR_TO_BTF_ID_OR_NULL : PTR_TO_BTF_ID;
 			regs[BPF_REG_0].btf_id = meta.ret_btf_id;
 		}
-	} else if (fn->ret_type == RET_PTR_TO_BTF_ID_OR_NULL) {
+	} else if (base_type(ret_type) == RET_PTR_TO_BTF_ID) {
 		int ret_btf_id;
 
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		regs[BPF_REG_0].type = PTR_TO_BTF_ID_OR_NULL;
 		ret_btf_id = *fn->ret_btf_id;
 		if (ret_btf_id == 0) {
-			verbose(env, "invalid return type %d of func %s#%d\n",
-				fn->ret_type, func_id_name(func_id), func_id);
+			verbose(env, "invalid return type %u of func %s#%d\n",
+				base_type(ret_type), func_id_name(func_id),
+				func_id);
 			return -EINVAL;
 		}
 		regs[BPF_REG_0].btf_id = ret_btf_id;
 	} else {
-		verbose(env, "unknown return type %d of func %s#%d\n",
-			fn->ret_type, func_id_name(func_id), func_id);
+		verbose(env, "unknown return type %u of func %s#%d\n",
+			base_type(ret_type), func_id_name(func_id), func_id);
 		return -EINVAL;
 	}