diff mbox series

[bpf-next,v4,1/6] bpf: Add MEM_UNINIT as a bpf_type_flag

Message ID 20220509224257.3222614-2-joannelkoong@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series Dynamic pointers | expand

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Context Check Description
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1467 this patch: 1467
netdev/cc_maintainers warning 6 maintainers not CCed: netdev@vger.kernel.org kafai@fb.com john.fastabend@gmail.com yhs@fb.com kpsingh@kernel.org songliubraving@fb.com
netdev/build_clang success Errors and warnings before: 174 this patch: 174
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1474 this patch: 1474
netdev/checkpatch warning WARNING: line length of 87 exceeds 80 columns
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-PR fail merge-conflict
bpf/vmtest-bpf-next-VM_Test-1 success Logs for Kernel LATEST on ubuntu-latest + selftests
bpf/vmtest-bpf-next-VM_Test-2 success Logs for Kernel LATEST on z15 + selftests

Commit Message

Joanne Koong May 9, 2022, 10:42 p.m. UTC 
Instead of having uninitialized versions of arguments as separate
bpf_arg_types (eg ARG_PTR_TO_UNINIT_MEM as the uninitialized version
of ARG_PTR_TO_MEM), we can instead use MEM_UNINIT as a bpf_type_flag
modifier to denote that the argument is uninitialized.

Doing so cleans up some of the logic in the verifier. We no longer
need to do two checks against an argument type (eg "if
(base_type(arg_type) == ARG_PTR_TO_MEM || base_type(arg_type) ==
ARG_PTR_TO_UNINIT_MEM)"), since uninitialized and initialized
versions of the same argument type will now share the same base type.

In the near future, MEM_UNINIT will be used by dynptr helper functions
as well.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
---
 include/linux/bpf.h   | 17 +++++++++--------
 kernel/bpf/helpers.c  |  4 ++--
 kernel/bpf/verifier.c | 28 ++++++++--------------------
 3 files changed, 19 insertions(+), 30 deletions(-)

Comments

David Vernet May 13, 2022, 2:11 p.m. UTC | #1 
On Mon, May 09, 2022 at 03:42:52PM -0700, Joanne Koong wrote:
> Instead of having uninitialized versions of arguments as separate
> bpf_arg_types (eg ARG_PTR_TO_UNINIT_MEM as the uninitialized version
> of ARG_PTR_TO_MEM), we can instead use MEM_UNINIT as a bpf_type_flag
> modifier to denote that the argument is uninitialized.
> 
> Doing so cleans up some of the logic in the verifier. We no longer
> need to do two checks against an argument type (eg "if
> (base_type(arg_type) == ARG_PTR_TO_MEM || base_type(arg_type) ==
> ARG_PTR_TO_UNINIT_MEM)"), since uninitialized and initialized
> versions of the same argument type will now share the same base type.
> 
> In the near future, MEM_UNINIT will be used by dynptr helper functions
> as well.
> 
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>

Looks great, thanks.

Acked-by: David Vernet <void@manifault.com>
diff mbox series

Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index be94833d390a..d0c167865504 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -389,7 +389,9 @@  enum bpf_type_flag {
 	 */
 	PTR_UNTRUSTED		= BIT(6 + BPF_BASE_TYPE_BITS),
 
-	__BPF_TYPE_LAST_FLAG	= PTR_UNTRUSTED,
+	MEM_UNINIT		= BIT(7 + BPF_BASE_TYPE_BITS),
+
+	__BPF_TYPE_LAST_FLAG	= MEM_UNINIT,
 };
 
 /* Max number of base types. */
@@ -408,16 +410,11 @@  enum bpf_arg_type {
 	ARG_CONST_MAP_PTR,	/* const argument used as pointer to bpf_map */
 	ARG_PTR_TO_MAP_KEY,	/* pointer to stack used as map key */
 	ARG_PTR_TO_MAP_VALUE,	/* pointer to stack used as map value */
-	ARG_PTR_TO_UNINIT_MAP_VALUE,	/* pointer to valid memory used to store a map value */
 
-	/* the following constraints used to prototype bpf_memcmp() and other
-	 * functions that access data on eBPF program stack
+	/* Used to prototype bpf_memcmp() and other functions that access data
+	 * on eBPF program stack
 	 */
 	ARG_PTR_TO_MEM,		/* pointer to valid memory (stack, packet, map value) */
-	ARG_PTR_TO_UNINIT_MEM,	/* pointer to memory does not need to be initialized,
-				 * helper function must fill all bytes or clear
-				 * them in error case.
-				 */
 
 	ARG_CONST_SIZE,		/* number of bytes accessed from memory */
 	ARG_CONST_SIZE_OR_ZERO,	/* number of bytes accessed from memory or 0 */
@@ -449,6 +446,10 @@  enum bpf_arg_type {
 	ARG_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | ARG_PTR_TO_ALLOC_MEM,
 	ARG_PTR_TO_STACK_OR_NULL	= PTR_MAYBE_NULL | ARG_PTR_TO_STACK,
 	ARG_PTR_TO_BTF_ID_OR_NULL	= PTR_MAYBE_NULL | ARG_PTR_TO_BTF_ID,
+	/* pointer to memory does not need to be initialized, helper function must fill
+	 * all bytes or clear them in error case.
+	 */
+	ARG_PTR_TO_UNINIT_MEM		= MEM_UNINIT | ARG_PTR_TO_MEM,
 
 	/* 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.
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 3e709fed5306..8a2398ac14c2 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -103,7 +103,7 @@  const struct bpf_func_proto bpf_map_pop_elem_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_CONST_MAP_PTR,
-	.arg2_type	= ARG_PTR_TO_UNINIT_MAP_VALUE,
+	.arg2_type	= ARG_PTR_TO_MAP_VALUE | MEM_UNINIT,
 };
 
 BPF_CALL_2(bpf_map_peek_elem, struct bpf_map *, map, void *, value)
@@ -116,7 +116,7 @@  const struct bpf_func_proto bpf_map_peek_elem_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_CONST_MAP_PTR,
-	.arg2_type	= ARG_PTR_TO_UNINIT_MAP_VALUE,
+	.arg2_type	= ARG_PTR_TO_MAP_VALUE | MEM_UNINIT,
 };
 
 const struct bpf_func_proto bpf_get_prandom_u32_proto = {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 813f6ee80419..0fe1dea520ae 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5378,12 +5378,6 @@  static int process_kptr_func(struct bpf_verifier_env *env, int regno,
 	return 0;
 }
 
-static bool arg_type_is_mem_ptr(enum bpf_arg_type type)
-{
-	return base_type(type) == ARG_PTR_TO_MEM ||
-	       base_type(type) == ARG_PTR_TO_UNINIT_MEM;
-}
-
 static bool arg_type_is_mem_size(enum bpf_arg_type type)
 {
 	return type == ARG_CONST_SIZE ||
@@ -5523,7 +5517,6 @@  static const struct bpf_reg_types kptr_types = { .types = { PTR_TO_MAP_VALUE } }
 static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
 	[ARG_PTR_TO_MAP_KEY]		= &map_key_value_types,
 	[ARG_PTR_TO_MAP_VALUE]		= &map_key_value_types,
-	[ARG_PTR_TO_UNINIT_MAP_VALUE]	= &map_key_value_types,
 	[ARG_CONST_SIZE]		= &scalar_types,
 	[ARG_CONST_SIZE_OR_ZERO]	= &scalar_types,
 	[ARG_CONST_ALLOC_SIZE_OR_ZERO]	= &scalar_types,
@@ -5537,7 +5530,6 @@  static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
 	[ARG_PTR_TO_BTF_ID]		= &btf_ptr_types,
 	[ARG_PTR_TO_SPIN_LOCK]		= &spin_lock_types,
 	[ARG_PTR_TO_MEM]		= &mem_types,
-	[ARG_PTR_TO_UNINIT_MEM]		= &mem_types,
 	[ARG_PTR_TO_ALLOC_MEM]		= &alloc_mem_types,
 	[ARG_PTR_TO_INT]		= &int_ptr_types,
 	[ARG_PTR_TO_LONG]		= &int_ptr_types,
@@ -5711,8 +5703,7 @@  static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		return -EACCES;
 	}
 
-	if (base_type(arg_type) == ARG_PTR_TO_MAP_VALUE ||
-	    base_type(arg_type) == ARG_PTR_TO_UNINIT_MAP_VALUE) {
+	if (base_type(arg_type) == ARG_PTR_TO_MAP_VALUE) {
 		err = resolve_map_arg_type(env, meta, &arg_type);
 		if (err)
 			return err;
@@ -5798,8 +5789,7 @@  static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		err = check_helper_mem_access(env, regno,
 					      meta->map_ptr->key_size, false,
 					      NULL);
-	} else if (base_type(arg_type) == ARG_PTR_TO_MAP_VALUE ||
-		   base_type(arg_type) == ARG_PTR_TO_UNINIT_MAP_VALUE) {
+	} else if (base_type(arg_type) == ARG_PTR_TO_MAP_VALUE) {
 		if (type_may_be_null(arg_type) && register_is_null(reg))
 			return 0;
 
@@ -5811,7 +5801,7 @@  static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			verbose(env, "invalid map_ptr to access map->value\n");
 			return -EACCES;
 		}
-		meta->raw_mode = (arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE);
+		meta->raw_mode = arg_type & MEM_UNINIT;
 		err = check_helper_mem_access(env, regno,
 					      meta->map_ptr->value_size, false,
 					      meta);
@@ -5838,11 +5828,11 @@  static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			return -EACCES;
 	} else if (arg_type == ARG_PTR_TO_FUNC) {
 		meta->subprogno = reg->subprogno;
-	} else if (arg_type_is_mem_ptr(arg_type)) {
+	} else if (base_type(arg_type) == ARG_PTR_TO_MEM) {
 		/* The access to this pointer is only checked when we hit the
 		 * next is_mem_size argument below.
 		 */
-		meta->raw_mode = (arg_type == ARG_PTR_TO_UNINIT_MEM);
+		meta->raw_mode = arg_type & MEM_UNINIT;
 	} else if (arg_type_is_mem_size(arg_type)) {
 		bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);
 
@@ -6189,10 +6179,8 @@  static bool check_raw_mode_ok(const struct bpf_func_proto *fn)
 static bool check_args_pair_invalid(enum bpf_arg_type arg_curr,
 				    enum bpf_arg_type arg_next)
 {
-	return (arg_type_is_mem_ptr(arg_curr) &&
-	        !arg_type_is_mem_size(arg_next)) ||
-	       (!arg_type_is_mem_ptr(arg_curr) &&
-		arg_type_is_mem_size(arg_next));
+	return (base_type(arg_curr) == ARG_PTR_TO_MEM) !=
+		arg_type_is_mem_size(arg_next);
 }
 
 static bool check_arg_pair_ok(const struct bpf_func_proto *fn)
@@ -6203,7 +6191,7 @@  static bool check_arg_pair_ok(const struct bpf_func_proto *fn)
 	 * helper function specification.
 	 */
 	if (arg_type_is_mem_size(fn->arg1_type) ||
-	    arg_type_is_mem_ptr(fn->arg5_type)  ||
+	    base_type(fn->arg5_type) == ARG_PTR_TO_MEM ||
 	    check_args_pair_invalid(fn->arg1_type, fn->arg2_type) ||
 	    check_args_pair_invalid(fn->arg2_type, fn->arg3_type) ||
 	    check_args_pair_invalid(fn->arg3_type, fn->arg4_type) ||