[PATCH bpf-next 0/2] bpf: Disallow BPF_F_LOCK with mixed special fields

[PATCH bpf-next 0/2] bpf: Disallow BPF_F_LOCK with mixed special fields

[Leon Hwang]

Disallow combining BPF_F_LOCK with map values that mix bpf_spin_lock and
other special BTF fields, which may lead to undefined behavior. Such cases
are now rejected with -EOPNOTSUPP.

Map update flag validation is centralized in
bpf_map_check_op_flags() and reused across array, hash, local-storage,
and task-storage update paths, with selftests added to verify the new
behavior.

Leon Hwang (2):
  bpf: Disallow BPF_F_LOCK with mixed special fields and centralize flag
    checks
  selftests/bpf: Add tests to verify BPF_F_LOCK restrictions

 include/linux/bpf.h                           |  7 ++
 kernel/bpf/arraymap.c                         | 11 ++-
 kernel/bpf/bpf_local_storage.c                |  7 --
 kernel/bpf/bpf_task_storage.c                 |  3 -
 kernel/bpf/hashtab.c                          |  8 +--
 .../selftests/bpf/prog_tests/map_lock.c       | 70 +++++++++++++++++++
 .../selftests/bpf/progs/test_map_lock.c       | 31 +++++++-
 7 files changed, 114 insertions(+), 23 deletions(-)

--
2.52.0

[PATCH bpf-next 1/2] bpf: Disallow BPF_F_LOCK with mixed special fields and centralize flag checks

[Leon Hwang]

Disallow combining BPF_F_LOCK with map values that contain special BTF
fields other than bpf_spin_lock (e.g. kptr or uptr). Such mixing may lead
to subtle or undefined behavior in map value updating. Reject these
combinations early by returning -EOPNOTSUPP.

Centralize map update flag validation in bpf_map_check_op_flags() and
reuse it across array, hash, local-storage, and task-storage map update
paths. Explicitly reject incompatible BPF_NOEXIST/BPF_EXIST combinations
and invalid BPF_F_LOCK usage to keep flag validation consistent and
eliminate duplicated per-map checks.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 include/linux/bpf.h            |  7 +++++++
 kernel/bpf/arraymap.c          | 11 ++++-------
 kernel/bpf/bpf_local_storage.c |  7 -------
 kernel/bpf/bpf_task_storage.c  |  3 ---
 kernel/bpf/hashtab.c           |  8 +++-----
 5 files changed, 14 insertions(+), 22 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5936f8e2996f..c5863487ee73 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -3935,9 +3935,16 @@ static inline int bpf_map_check_op_flags(struct bpf_map *map, u64 flags, u64 all
 	if ((u32)flags & ~allowed_flags)
 		return -EINVAL;
 
+	/* BPF_NOEXIST and BPF_EXIST are mutually exclusive. */
+	if ((flags & (BPF_NOEXIST | BPF_EXIST)) == (BPF_NOEXIST | BPF_EXIST))
+		return -EINVAL;
+
 	if ((flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK))
 		return -EINVAL;
 
+	if ((flags & BPF_F_LOCK) && btf_record_has_field(map->record, ~BPF_SPIN_LOCK))
+		return -EOPNOTSUPP;
+
 	if (!(flags & BPF_F_CPU) && flags >> 32)
 		return -EINVAL;
 
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 67e9e811de3a..1cff40f109cd 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -366,10 +366,7 @@ static long array_map_update_elem(struct bpf_map *map, void *key, void *value,
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
 	u32 index = *(u32 *)key;
 	char *val;
-
-	if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST))
-		/* unknown flags */
-		return -EINVAL;
+	int err;
 
 	if (unlikely(index >= array->map.max_entries))
 		/* all elements were pre-allocated, cannot insert a new one */
@@ -379,9 +376,9 @@ static long array_map_update_elem(struct bpf_map *map, void *key, void *value,
 		/* all elements already exist */
 		return -EEXIST;
 
-	if (unlikely((map_flags & BPF_F_LOCK) &&
-		     !btf_record_has_field(map->record, BPF_SPIN_LOCK)))
-		return -EINVAL;
+	err = bpf_map_check_op_flags(map, map_flags, BPF_EXIST | BPF_F_LOCK);
+	if (unlikely(err))
+		return err;
 
 	if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY) {
 		val = this_cpu_ptr(array->pptrs[index & array->index_mask]);
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index e2fe6c32822b..80b50091cbbf 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -493,13 +493,6 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
 	unsigned long flags;
 	int err;
 
-	/* BPF_EXIST and BPF_NOEXIST cannot be both set */
-	if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
-	    /* BPF_F_LOCK can only be used in a value with spin_lock */
-	    unlikely((map_flags & BPF_F_LOCK) &&
-		     !btf_record_has_field(smap->map.record, BPF_SPIN_LOCK)))
-		return ERR_PTR(-EINVAL);
-
 	if (gfp_flags == GFP_KERNEL && (map_flags & ~BPF_F_LOCK) != BPF_NOEXIST)
 		return ERR_PTR(-EINVAL);
 
diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index a1dc1bf0848a..21d84818e64e 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -125,9 +125,6 @@ static long bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
 	struct pid *pid;
 	int fd, err;
 
-	if ((map_flags & BPF_F_LOCK) && btf_record_has_field(map->record, BPF_UPTR))
-		return -EOPNOTSUPP;
-
 	fd = *(int *)key;
 	pid = pidfd_get_pid(fd, &f_flags);
 	if (IS_ERR(pid))
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 3b9d297a53be..2f6ed3e80308 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1093,9 +1093,9 @@ static long htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 	u32 key_size, hash;
 	int ret;
 
-	if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST))
-		/* unknown flags */
-		return -EINVAL;
+	ret = bpf_map_check_op_flags(map, map_flags, BPF_NOEXIST | BPF_EXIST | BPF_F_LOCK);
+	if (unlikely(ret))
+		return ret;
 
 	WARN_ON_ONCE(!bpf_rcu_lock_held());
 
@@ -1107,8 +1107,6 @@ static long htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 	head = &b->head;
 
 	if (unlikely(map_flags & BPF_F_LOCK)) {
-		if (unlikely(!btf_record_has_field(map->record, BPF_SPIN_LOCK)))
-			return -EINVAL;
 		/* find an element without taking the bucket lock */
 		l_old = lookup_nulls_elem_raw(head, hash, key, key_size,
 					      htab->n_buckets);
-- 
2.52.0

[PATCH bpf-next 2/2] selftests/bpf: Add tests to verify BPF_F_LOCK restrictions

[Leon Hwang]

Add a tc-based helper program that updates a map value containing both
bpf_spin_lock and bpf_timer and records errors for invalid flag
combinations.

Extend the existing map_lock tests to cover array and hash maps. Verify
that BPF_NOEXIST|BPF_EXIST is rejected with -EINVAL/-EEXIST, and that
BPF_F_LOCK returns -EOPNOTSUPP when mixed with other special fields.

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 .../selftests/bpf/prog_tests/map_lock.c       | 70 +++++++++++++++++++
 .../selftests/bpf/progs/test_map_lock.c       | 31 +++++++-
 2 files changed, 100 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/map_lock.c b/tools/testing/selftests/bpf/prog_tests/map_lock.c
index 1d6726f01dd2..aafae8d02e1d 100644
--- a/tools/testing/selftests/bpf/prog_tests/map_lock.c
+++ b/tools/testing/selftests/bpf/prog_tests/map_lock.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <test_progs.h>
 #include <network_helpers.h>
+#include "test_map_lock.skel.h"
 
 static void *spin_lock_thread(void *arg)
 {
@@ -90,3 +91,72 @@ void test_map_lock(void)
 close_prog:
 	bpf_object__close(obj);
 }
+
+struct map_value {
+	struct bpf_spin_lock lock;
+	struct bpf_timer timer;
+	__u64 payload;
+};
+
+static void test_map_lock_update_elem(enum bpf_map_type map_type, int err_exist)
+{
+	struct map_value val = {};
+	struct test_map_lock *skel;
+	int prog_fd, err;
+	u32 key = 0;
+	char buff[128] = {};
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		    .data_in = buff,
+		    .data_size_in = sizeof(buff),
+		    .repeat = 1,
+	);
+
+	skel = test_map_lock__open();
+	if (!ASSERT_OK_PTR(skel, "test_map_lock__open"))
+		return;
+
+	bpf_map__set_type(skel->maps.map, map_type);
+
+	err = test_map_lock__load(skel);
+	if (!ASSERT_OK(err, "test_map_lock__load"))
+		goto out;
+
+	err = bpf_map__update_elem(skel->maps.map, &key, sizeof(key), &val, sizeof(val),
+				   BPF_NOEXIST | BPF_EXIST);
+	if (!ASSERT_EQ(err, -EINVAL, "err_exist"))
+		goto out;
+
+	err = bpf_map__update_elem(skel->maps.map, &key, sizeof(key), &val, sizeof(val),
+				   BPF_F_LOCK);
+	if (!ASSERT_EQ(err, -EOPNOTSUPP, "err_lock"))
+		goto out;
+
+	prog_fd = bpf_program__fd(skel->progs.map_update);
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	if (!ASSERT_OK(err, "bpf_prog_test_run_opts"))
+		goto out;
+
+	ASSERT_EQ(skel->bss->err_exist, err_exist, "err_exist");
+	ASSERT_EQ(skel->bss->err_lock, -EOPNOTSUPP, "err_lock");
+
+out:
+	test_map_lock__destroy(skel);
+}
+
+static void test_array_map_lock_update_elem(void)
+{
+	test_map_lock_update_elem(BPF_MAP_TYPE_ARRAY, -EEXIST);
+}
+
+static void test_hash_map_lock_update_elem(void)
+{
+	test_map_lock_update_elem(BPF_MAP_TYPE_HASH, -EINVAL);
+}
+
+void test_map_lock_flag(void)
+{
+	if (test__start_subtest("array_map"))
+		test_array_map_lock_update_elem();
+	if (test__start_subtest("hash_map"))
+		test_hash_map_lock_update_elem();
+}
diff --git a/tools/testing/selftests/bpf/progs/test_map_lock.c b/tools/testing/selftests/bpf/progs/test_map_lock.c
index 1c02511b73cd..f1b7b741795c 100644
--- a/tools/testing/selftests/bpf/progs/test_map_lock.c
+++ b/tools/testing/selftests/bpf/progs/test_map_lock.c
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 // Copyright (c) 2019 Facebook
-#include <linux/bpf.h>
+#include "vmlinux.h"
 #include <linux/version.h>
 #include <bpf/bpf_helpers.h>
 
@@ -59,4 +59,33 @@ int bpf_map_lock_test(struct __sk_buff *skb)
 err:
 	return err;
 }
+
+int err_exist;
+int err_lock;
+
+struct map_value {
+	struct bpf_spin_lock lock;
+	struct bpf_timer timer;
+	__u64 payload;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, u32);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+} map SEC(".maps");
+
+SEC("tc")
+int map_update(struct __sk_buff *skb)
+{
+	struct map_value val = {};
+	u32 key = 0;
+
+	val.payload = 0xDEADBEEF;
+	err_exist = bpf_map_update_elem(&map, &key, &val, BPF_NOEXIST | BPF_EXIST);
+	err_lock = bpf_map_update_elem(&map, &key, &val, BPF_F_LOCK);
+	return BPF_OK;
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.52.0

Re: [PATCH bpf-next 1/2] bpf: Disallow BPF_F_LOCK with mixed special fields and centralize flag checks

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 2925 bytes --]

> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 5936f8e2996f..c5863487ee73 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -3935,9 +3935,16 @@ static inline int bpf_map_check_op_flags(struct bpf_map *map, u64 flags, u64 all
>  	if ((u32)flags & ~allowed_flags)
>  		return -EINVAL;
>
> +	/* BPF_NOEXIST and BPF_EXIST are mutually exclusive. */
> +	if ((flags & (BPF_NOEXIST | BPF_EXIST)) == (BPF_NOEXIST | BPF_EXIST))
> +		return -EINVAL;
> +
>  	if ((flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK))
>  		return -EINVAL;
>
> +	if ((flags & BPF_F_LOCK) && btf_record_has_field(map->record, ~BPF_SPIN_LOCK))
> +		return -EOPNOTSUPP;
> +
>  	if (!(flags & BPF_F_CPU) && flags >> 32)
>  		return -EINVAL;

[ ... ]

> diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
> index e2fe6c32822b..80b50091cbbf 100644
> --- a/kernel/bpf/bpf_local_storage.c
> +++ b/kernel/bpf/bpf_local_storage.c
> @@ -493,13 +493,6 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
>  	unsigned long flags;
>  	int err;
>
> -	/* BPF_EXIST and BPF_NOEXIST cannot be both set */
> -	if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
> -	    /* BPF_F_LOCK can only be used in a value with spin_lock */
> -	    unlikely((map_flags & BPF_F_LOCK) &&
> -		     !btf_record_has_field(smap->map.record, BPF_SPIN_LOCK)))
> -		return ERR_PTR(-EINVAL);
                ^^^^

This validation was removed from bpf_local_storage_update() but it appears
that no call to bpf_map_check_op_flags() was added in the local storage map
update functions. For array and hash maps, calls to bpf_map_check_op_flags()
were added in array_map_update_elem() and htab_map_update_elem(). However,
the local storage update functions like bpf_cgrp_storage_update_elem(),
bpf_fd_inode_storage_update_elem(), and bpf_fd_sk_storage_update_elem() pass
map_flags directly to bpf_local_storage_update() without calling
bpf_map_check_op_flags() first.

The syscall path does call bpf_map_check_op_flags() in map_update_elem() with
allowed_flags set to ~0, which catches the NOEXIST/EXIST mutual exclusion and
BPF_F_LOCK validation. But with allowed_flags=~0, the check for unknown flags
((u32)flags & ~allowed_flags) always passes zero, meaning unknown flags like
8 or 16 would not be rejected.

The old check (map_flags & ~BPF_F_LOCK) > BPF_EXIST rejected any unknown flag
bits. Is there a missing call to bpf_map_check_op_flags() in the local storage
update functions that should specify the allowed flags?

> -
>  	if (gfp_flags == GFP_KERNEL && (map_flags & ~BPF_F_LOCK) != BPF_NOEXIST)
>  		return ERR_PTR(-EINVAL);

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/21254704407

Re: [PATCH bpf-next 1/2] bpf: Disallow BPF_F_LOCK with mixed special fields and centralize flag checks

[Leon Hwang]

On 2026/1/23 00:02, bot+bpf-ci@kernel.org wrote:
>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
>> index 5936f8e2996f..c5863487ee73 100644
>> --- a/include/linux/bpf.h
>> +++ b/include/linux/bpf.h
>> @@ -3935,9 +3935,16 @@ static inline int bpf_map_check_op_flags(struct bpf_map *map, u64 flags, u64 all
>>  	if ((u32)flags & ~allowed_flags)
>>  		return -EINVAL;
>>
>> +	/* BPF_NOEXIST and BPF_EXIST are mutually exclusive. */
>> +	if ((flags & (BPF_NOEXIST | BPF_EXIST)) == (BPF_NOEXIST | BPF_EXIST))
>> +		return -EINVAL;
>> +
>>  	if ((flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK))
>>  		return -EINVAL;
>>
>> +	if ((flags & BPF_F_LOCK) && btf_record_has_field(map->record, ~BPF_SPIN_LOCK))
>> +		return -EOPNOTSUPP;
>> +
>>  	if (!(flags & BPF_F_CPU) && flags >> 32)
>>  		return -EINVAL;
> 
> [ ... ]
> 
>> diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
>> index e2fe6c32822b..80b50091cbbf 100644
>> --- a/kernel/bpf/bpf_local_storage.c
>> +++ b/kernel/bpf/bpf_local_storage.c
>> @@ -493,13 +493,6 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
>>  	unsigned long flags;
>>  	int err;
>>
>> -	/* BPF_EXIST and BPF_NOEXIST cannot be both set */
>> -	if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
>> -	    /* BPF_F_LOCK can only be used in a value with spin_lock */
>> -	    unlikely((map_flags & BPF_F_LOCK) &&
>> -		     !btf_record_has_field(smap->map.record, BPF_SPIN_LOCK)))
>> -		return ERR_PTR(-EINVAL);
>                 ^^^^
> 
> This validation was removed from bpf_local_storage_update() but it appears
> that no call to bpf_map_check_op_flags() was added in the local storage map
> update functions. For array and hash maps, calls to bpf_map_check_op_flags()
> were added in array_map_update_elem() and htab_map_update_elem(). However,
> the local storage update functions like bpf_cgrp_storage_update_elem(),
> bpf_fd_inode_storage_update_elem(), and bpf_fd_sk_storage_update_elem() pass
> map_flags directly to bpf_local_storage_update() without calling
> bpf_map_check_op_flags() first.
> 
> The syscall path does call bpf_map_check_op_flags() in map_update_elem() with
> allowed_flags set to ~0, which catches the NOEXIST/EXIST mutual exclusion and
> BPF_F_LOCK validation. But with allowed_flags=~0, the check for unknown flags
> ((u32)flags & ~allowed_flags) always passes zero, meaning unknown flags like
> 8 or 16 would not be rejected.
> 

Correct.

Such flags should indeed be rejected in the local storage update path.

Thanks,
Leon


> The old check (map_flags & ~BPF_F_LOCK) > BPF_EXIST rejected any unknown flag
> bits. Is there a missing call to bpf_map_check_op_flags() in the local storage
> update functions that should specify the allowed flags?
> 
>> -
>>  	if (gfp_flags == GFP_KERNEL && (map_flags & ~BPF_F_LOCK) != BPF_NOEXIST)
>>  		return ERR_PTR(-EINVAL);
> 
> [ ... ]
> 
> 
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
> 
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/21254704407