[PATCH bpf v4 0/3] bpf: Fix incorrect handling of user flags by percpu map updates

[PATCH bpf v4 0/3] bpf: Fix incorrect handling of user flags by percpu map updates

[Masoud Aghasi]

For BPF_MAP_TYPE_PERCPU_ARRAY map, bpf_percpu_array_update()
is not considering the possibility of a combination of
(BPF_NOEXIST, BPF_EXIST) flags with (BPF_F_CPU, BPF_F_ALL_CPUS) flags.
This causes the (BPF_NOEXIST, BPF_EXIST) flags to lose their effect
in some cases.

For BPF_MAP_TYPE_PERCPU_HASH and BPF_MAP_TYPE_LRU_PERCPU_HASH maps,
htab_map_check_update_flags() and check_flags() are not considering
the possibility of a combination of (BPF_NOEXIST, BPF_EXIST) flags
with (BPF_F_CPU, BPF_F_ALL_CPUS) flags. This causes the
(BPF_NOEXIST, BPF_EXIST) flags to lose their effect in some cases.

For example, when using (BPF_F_CPU | BPF_EXIST) flag combination
with bpf_map_update_elem() on a BPF_MAP_TYPE_PERCPU_HASH map, the
BPF_EXIST flag does not prevent new insertions as expected.

This series fixes the bug by adding proper flag validations and checks
and adds regression tests.

V4 changes:
- Edit selftest to use proper value_sz in the new cgroup map test
- Edit selftest to pin the current pid to the current cpu for LRU map
- Edit commit messages to include user-visible changes

V3 changes:
- Split the fix into two separate patches for array map and hash maps
- Extend the selftest to cover all percpu map types
- Extend the selftest to cover all applicable flag combinations
- Extend the selftest to cover the unnecessary delete issue of LRU map

V2 changes:
- Fix a BPF_EXIST flag check in __htab_lru_percpu_map_update_elem()
- Add additional test for BPF_MAP_TYPE_LRU_PERCPU_HASH map
- Add check for BPF_EXIST, BPF_NOEXIST combination in percpu array map

Masoud Aghasi (3):
  bpf: Fix incorrect handling of user flags in bpf_percpu_array_update
  bpf: Fix incorrect handling of user flags by percpu hash map updates
  selftests/bpf: add tests for percpu map flags combination

 kernel/bpf/arraymap.c                         |   5 +-
 kernel/bpf/hashtab.c                          |  11 +-
 .../selftests/bpf/prog_tests/percpu_alloc.c   | 200 ++++++++++++++++++
 3 files changed, 210 insertions(+), 6 deletions(-)

-- 
2.47.3

[PATCH bpf v4 1/3] bpf: Fix incorrect handling of user flags in bpf_percpu_array_update

[Masoud Aghasi]

For BPF_MAP_TYPE_PERCPU_ARRAY map, bpf_percpu_array_update()
is not considering the possibility of a combination of
(BPF_NOEXIST, BPF_EXIST) flags with (BPF_F_CPU, BPF_F_ALL_CPUS) flags.
This causes the (BPF_NOEXIST, BPF_EXIST) flags to lose their effect
in some cases.

For example, using the (BPF_F_ALL_CPUS | BPF_EXIST) flag combination
with bpf_map_update_elem() results in an incorrect EINVAL error
response, even though the flag combination is valid.

This patch fixes the bug by adding proper flag validations and checks.
Before this patch, bpf_percpu_array_update() rejected
BPF_F_ALL_CPUS | BPF_EXIST and BPF_F_ALL_CPUS | BPF_NOEXIST with
-EINVAL. Also the BPF_F_CPU | BPF_NOEXIST were accepted.
After the patch BPF_F_ALL_CPUS | BPF_EXIST is accepted and
BPF_F_ALL_CPUS | BPF_NOEXIST and BPF_F_CPU | BPF_NOEXIST
result in -EEXIST.

Fixes: 8eb76cb03f0f ("bpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu_array maps")
Signed-off-by: Masoud Aghasi <maghasi@disroot.org>
---
 kernel/bpf/arraymap.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 0fe9afd4a591..4edfde6a624c 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -438,7 +438,8 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
 	u32 size;
 	int cpu, off = 0;
 
-	if (unlikely((map_flags & BPF_F_LOCK) || (u32)map_flags > BPF_F_ALL_CPUS))
+	if (unlikely((map_flags & BPF_EXIST) && (map_flags & BPF_NOEXIST)) ||
+	    unlikely((u32)map_flags & ~(BPF_EXIST | BPF_NOEXIST | BPF_F_CPU | BPF_F_ALL_CPUS)))
 		/* unknown flags */
 		return -EINVAL;
 
@@ -446,7 +447,7 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
 		/* all elements were pre-allocated, cannot insert a new one */
 		return -E2BIG;
 
-	if (unlikely(map_flags == BPF_NOEXIST))
+	if (unlikely(map_flags & BPF_NOEXIST))
 		/* all elements already exist */
 		return -EEXIST;
 
-- 
2.47.3

Re: [PATCH bpf v4 1/3] bpf: Fix incorrect handling of user flags in bpf_percpu_array_update

[Leon Hwang]

Hi Masoud,

Please wait some time, say 24 hours, for human reviews before sending
the next revision.

On 4/10/26 19:10, Masoud Aghasi wrote:
> For BPF_MAP_TYPE_PERCPU_ARRAY map, bpf_percpu_array_update()
> is not considering the possibility of a combination of
> (BPF_NOEXIST, BPF_EXIST) flags with (BPF_F_CPU, BPF_F_ALL_CPUS) flags.
> This causes the (BPF_NOEXIST, BPF_EXIST) flags to lose their effect
> in some cases.

[...]

> @@ -438,7 +438,8 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
>  	u32 size;
>  	int cpu, off = 0;
>  
> -	if (unlikely((map_flags & BPF_F_LOCK) || (u32)map_flags > BPF_F_ALL_CPUS))
> +	if (unlikely((map_flags & BPF_EXIST) && (map_flags & BPF_NOEXIST)) ||
> +	    unlikely((u32)map_flags & ~(BPF_EXIST | BPF_NOEXIST | BPF_F_CPU | BPF_F_ALL_CPUS)))

Probably, we can add these two macros in include/linux/bpf.h.

#define BPF_EXIST_FLAGS (BPF_EXIST | BPF_NOEXIST)
#define BPF_CPU_FLAGS (BPF_F_CPU | BPF_F_ALL_CPUS)

Then, this 'if' can be simplified to

if (unlikely(((map_flags & BPF_EXIST_FLAGS) == BPF_EXIST_FLAGS) ||
	     ((u32)map_flags & ~(BPF_EXIST_FLAGS | BPF_CPU_FLAGS)))

Also simplify htab_map_check_update_flags() in the next patch by the
same way.

Thanks,
Leon

>  		/* unknown flags */
>  		return -EINVAL;
>  
> @@ -446,7 +447,7 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
>  		/* all elements were pre-allocated, cannot insert a new one */
>  		return -E2BIG;
>  
> -	if (unlikely(map_flags == BPF_NOEXIST))
> +	if (unlikely(map_flags & BPF_NOEXIST))
>  		/* all elements already exist */
>  		return -EEXIST;
>  

Re: [PATCH bpf v4 1/3] bpf: Fix incorrect handling of user flags in bpf_percpu_array_update

[Masoud Aghasi]

On 05/10/2026 04:10, Leon Hwang wrote:
> Hi Masoud,
> 
> Please wait some time, say 24 hours, for human reviews before sending
> the next revision.

Hi Leon, noted. thanks for the review.

> 
>> @@ -438,7 +438,8 @@ int bpf_percpu_array_update(struct bpf_map *map, void *key, void *value,
>>  	u32 size;
>>  	int cpu, off = 0;
>>  
>> -	if (unlikely((map_flags & BPF_F_LOCK) || (u32)map_flags > BPF_F_ALL_CPUS))
>> +	if (unlikely((map_flags & BPF_EXIST) && (map_flags & BPF_NOEXIST)) ||
>> +	    unlikely((u32)map_flags & ~(BPF_EXIST | BPF_NOEXIST | BPF_F_CPU | BPF_F_ALL_CPUS)))
> 
> Probably, we can add these two macros in include/linux/bpf.h.
> 
> #define BPF_EXIST_FLAGS (BPF_EXIST | BPF_NOEXIST)
> #define BPF_CPU_FLAGS (BPF_F_CPU | BPF_F_ALL_CPUS)
> 
> Then, this 'if' can be simplified to
> 
> if (unlikely(((map_flags & BPF_EXIST_FLAGS) == BPF_EXIST_FLAGS) ||
> 	     ((u32)map_flags & ~(BPF_EXIST_FLAGS | BPF_CPU_FLAGS)))
> 
> Also simplify htab_map_check_update_flags() in the next patch by the
> same way.
> 
> Thanks,
> Leon

Sounds good to me. I will apply it to the v5 if there are no objections.

[PATCH bpf v4 2/3] bpf: Fix incorrect handling of user flags by percpu hash map updates

[Masoud Aghasi]

For BPF_MAP_TYPE_PERCPU_HASH and BPF_MAP_TYPE_LRU_PERCPU_HASH maps,
htab_map_check_update_flags() and check_flags() are not considering
the possibility of a combination of (BPF_NOEXIST, BPF_EXIST) flags
with (BPF_F_CPU, BPF_F_ALL_CPUS) flags. This causes the
(BPF_NOEXIST, BPF_EXIST) flags to lose their effect in some cases.

For example, when using (BPF_F_CPU | BPF_EXIST) or
(BPF_F_CPU | BPF_NOEXIST) flag combinations with bpf_map_update_elem()
on a percpu hash map, the BPF_EXIST flag does not prevent new
insertions as expected and BPF_NOEXIST flag does not prevent
modification of existing entries as expected.

This patch fixes the bug by adding proper flag validations and checks.
Before this patch, htab_map_check_update_flags() rejected
(BPF_F_ALL_CPUS | BPF_EXIST) and (BPF_F_ALL_CPUS | BPF_NOEXIST) with
-EINVAL. After the patch those combinations are accepted.

This patch also starts returning -EINVAL for (BPF_EXIST | BPF_NOEXIST),
with or without BPF_F_CPU, which was previously accepted.

Fixes: c6936161fd55 ("bpf: Add BPF_F_CPU and BPF_F_ALL_CPUS flags support for percpu_hash and lru_percpu_hash maps")
Signed-off-by: Masoud Aghasi <maghasi@disroot.org>
---
 kernel/bpf/hashtab.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 53c99fe4f176..2106b82894b2 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1196,11 +1196,11 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
 static int check_flags(struct bpf_htab *htab, struct htab_elem *l_old,
 		       u64 map_flags)
 {
-	if (l_old && (map_flags & ~BPF_F_LOCK) == BPF_NOEXIST)
+	if (l_old && (map_flags & BPF_NOEXIST))
 		/* elem already exists */
 		return -EEXIST;
 
-	if (!l_old && (map_flags & ~BPF_F_LOCK) == BPF_EXIST)
+	if (!l_old && (map_flags & BPF_EXIST))
 		/* elem doesn't exist, cannot update it */
 		return -ENOENT;
 
@@ -1383,9 +1383,12 @@ static long htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value
 
 static int htab_map_check_update_flags(bool onallcpus, u64 map_flags)
 {
+	if (unlikely((map_flags & BPF_EXIST) && (map_flags & BPF_NOEXIST)))
+		return -EINVAL;
 	if (unlikely(!onallcpus && map_flags > BPF_EXIST))
 		return -EINVAL;
-	if (unlikely(onallcpus && ((map_flags & BPF_F_LOCK) || (u32)map_flags > BPF_F_ALL_CPUS)))
+	if (unlikely(onallcpus &&
+	    ((u32)map_flags & ~(BPF_EXIST | BPF_NOEXIST | BPF_F_CPU | BPF_F_ALL_CPUS))))
 		return -EINVAL;
 	return 0;
 }
@@ -1483,7 +1486,7 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
 	 * to remove older elem from htab and this removal
 	 * operation will need a bucket lock.
 	 */
-	if (map_flags != BPF_EXIST) {
+	if (!(map_flags & BPF_EXIST)) {
 		l_new = prealloc_lru_pop(htab, key, hash);
 		if (!l_new)
 			return -ENOMEM;
-- 
2.47.3

[PATCH bpf v4 3/3] selftests/bpf: add tests for percpu map flags combination

[Masoud Aghasi]

All possible combinations of (BPF_EXIST, BPF_NOEXIST) and
(BPF_F_ALL_CPUS, BPF_F_CPU) flags are covered for all percpu map types.

As BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE does not support BPF_NOEXIST and
also in order to reduce the amount of code duplicates, I added its
new test scenarios to the existing cpu_flag_percpu_cgroup_storage test.

But for other percpu map types, I added new tests to be able to
exercise all flag combinations and the edge cases such as percpu LRU
unnecessary deletion issue.

Signed-off-by: Masoud Aghasi <maghasi@disroot.org>
---
 .../selftests/bpf/prog_tests/percpu_alloc.c   | 200 ++++++++++++++++++
 1 file changed, 200 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c b/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c
index 7b4a1e24363b..1f33ea20d845 100644
--- a/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c
@@ -449,6 +449,48 @@ static void test_lru_percpu_hash_cpu_flag_create(void)
 	test_percpu_map_cpu_flag_create(BPF_MAP_TYPE_LRU_PERCPU_HASH, 0);
 }
 
+static void test_percpu_cgroup_storage_flags_combination(struct bpf_map *map, int nr_cpus,
+							  struct bpf_cgroup_storage_key *key)
+{
+	int err;
+	u64 flags = 0;
+	size_t value_sz = sizeof(u32);
+	size_t elem_sz = roundup(value_sz, 8);
+	u32 *values = NULL;
+
+	values = calloc(nr_cpus, elem_sz);
+	if (!ASSERT_OK_PTR(values, "calloc values"))
+		return;
+
+	flags = BPF_NOEXIST | BPF_EXIST;
+	err = bpf_map__update_elem(map, key, sizeof(*key), values, elem_sz * nr_cpus, flags);
+	if (!ASSERT_EQ(err, -EINVAL, "bpf_map__update_elem noexist|exist"))
+		goto out;
+
+	flags = BPF_F_ALL_CPUS | BPF_NOEXIST;
+	err = bpf_map__update_elem(map, key, sizeof(*key), values, value_sz, flags);
+	if (!ASSERT_EQ(err, -EINVAL, "bpf_map__update_elem all_cpus|noexist"))
+		goto out;
+
+	flags = BPF_F_CPU | BPF_NOEXIST;
+	err = bpf_map__update_elem(map, key, sizeof(*key), values, value_sz, flags);
+	if (!ASSERT_EQ(err, -EINVAL, "bpf_map__update_elem cpu|noexist"))
+		goto out;
+
+	flags = BPF_F_ALL_CPUS | BPF_EXIST;
+	err = bpf_map__update_elem(map, key, sizeof(*key), values, value_sz, flags);
+	if (!ASSERT_OK(err, "bpf_map__update_elem all_cpus|exist"))
+		goto out;
+
+	flags = BPF_F_CPU | BPF_EXIST;
+	err = bpf_map__update_elem(map, key, sizeof(*key), values, value_sz, flags);
+	if (!ASSERT_OK(err, "bpf_map__update_elem cpu|exist"))
+		goto out;
+
+out:
+	free(values);
+}
+
 static void test_percpu_cgroup_storage_cpu_flag(void)
 {
 	struct percpu_alloc_array *skel = NULL;
@@ -489,6 +531,7 @@ static void test_percpu_cgroup_storage_cpu_flag(void)
 		goto out;
 
 	test_percpu_map_op_cpu_flag(map, &key, sizeof(key), 1, nr_cpus, false);
+	test_percpu_cgroup_storage_flags_combination(map, nr_cpus, &key);
 out:
 	bpf_prog_detach2(-1, cgroup, BPF_CGROUP_INET_EGRESS);
 	close(cgroup);
@@ -537,6 +580,157 @@ static void test_hash_cpu_flag(void)
 	test_map_op_cpu_flag(BPF_MAP_TYPE_HASH);
 }
 
+static void test_percpu_map_flags_combination(enum bpf_map_type map_type)
+{
+	size_t value_sz = 8;
+	void *values = NULL;
+	u32 max_entries = 3, key = 0;
+	u64 flags = 0;
+	int err, map_fd, nr_cpus;
+	bool is_hash_map = (map_type == BPF_MAP_TYPE_PERCPU_HASH ||
+			    map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
+
+	nr_cpus = libbpf_num_possible_cpus();
+	if (!ASSERT_GT(nr_cpus, 0, "libbpf_num_possible_cpus"))
+		return;
+
+	values = calloc(nr_cpus, value_sz);
+	if (!ASSERT_OK_PTR(values, "calloc values"))
+		return;
+
+	map_fd = bpf_map_create(map_type, "test_flags_combination_map",
+				sizeof(u32), value_sz, max_entries, NULL);
+	if (!ASSERT_GE(map_fd, 0, "bpf_map_create")) {
+		free(values);
+		return;
+	}
+
+	flags = BPF_NOEXIST | BPF_EXIST;
+	err = bpf_map_update_elem(map_fd, &key, values, flags);
+	if (!ASSERT_EQ(err, -EINVAL, "bpf_map_update_elem noexist|exist"))
+		goto out;
+
+	flags = BPF_F_ALL_CPUS | BPF_NOEXIST;
+	key = 0;
+	err = bpf_map_update_elem(map_fd, &key, values, flags);
+	if (is_hash_map) {
+		if (!ASSERT_OK(err, "bpf_map_update_elem all_cpus|noexist"))
+			goto out;
+
+		err = bpf_map_update_elem(map_fd, &key, values, flags);
+		if (!ASSERT_EQ(err, -EEXIST, "bpf_map_update_elem all_cpus|noexist"))
+			goto out;
+	} else {
+		if (!ASSERT_EQ(err, -EEXIST, "bpf_map_update_elem all_cpus|noexist"))
+			goto out;
+	}
+
+	flags = BPF_F_CPU | BPF_NOEXIST;
+	key = 1;
+	err = bpf_map_update_elem(map_fd, &key, values, flags);
+	if (is_hash_map) {
+		if (!ASSERT_OK(err, "bpf_map_update_elem cpu|noexist"))
+			goto out;
+
+		err = bpf_map_update_elem(map_fd, &key, values, flags);
+		if (!ASSERT_EQ(err, -EEXIST, "bpf_map_update_elem cpu|noexist"))
+			goto out;
+	} else {
+		if (!ASSERT_EQ(err, -EEXIST, "bpf_map_update_elem cpu|noexist"))
+			goto out;
+	}
+
+	flags = BPF_F_ALL_CPUS | BPF_EXIST;
+	key = 2;
+	err = bpf_map_update_elem(map_fd, &key, values, flags);
+	if (is_hash_map) {
+		if (!ASSERT_EQ(err, -ENOENT, "bpf_map_update_elem all_cpus|exist"))
+			goto out;
+	} else {
+		if (!ASSERT_OK(err, "bpf_map_update_elem all_cpus|exist"))
+			goto out;
+	}
+
+	flags = BPF_F_CPU | BPF_EXIST;
+	err = bpf_map_update_elem(map_fd, &key, values, flags);
+	if (is_hash_map) {
+		if (!ASSERT_EQ(err, -ENOENT, "bpf_map_update_elem cpu|exist"))
+			goto out;
+	} else {
+		if (!ASSERT_OK(err, "bpf_map_update_elem cpu|exist"))
+			goto out;
+	}
+
+	if (map_type != BPF_MAP_TYPE_LRU_PERCPU_HASH)
+		goto out;
+
+	/* Percpu LRU hash map should not delete old entries unnecessarily */
+	flags = BPF_F_ALL_CPUS | BPF_NOEXIST;
+	key = 2;
+	err = bpf_map_update_elem(map_fd, &key, values, flags);
+	if (!ASSERT_OK(err, "bpf_map_update_elem unnecessary_deletion"))
+		goto out;
+
+	flags = BPF_F_ALL_CPUS | BPF_EXIST;
+	err = bpf_map_update_elem(map_fd, &key, values, flags);
+	if (!ASSERT_OK(err, "bpf_map_update_elem unnecessary_deletion"))
+		goto out;
+
+	key = 0;
+	err = bpf_map_lookup_elem(map_fd, &key, values);
+	if (!ASSERT_OK(err, "bpf_map_lookup_elem unnecessary_deletion"))
+		goto out;
+
+out:
+	close(map_fd);
+	free(values);
+}
+
+static int pin_current_cpu(cpu_set_t *old_mask)
+{
+	int err, cpu;
+	cpu_set_t new_mask;
+
+	err = sched_getaffinity(0, sizeof(*old_mask), old_mask);
+	if (!ASSERT_OK(err, "sched_getaffinity"))
+		return -1;
+
+	cpu = sched_getcpu();
+	if (!ASSERT_GE(cpu, 0, "sched_getcpu"))
+		return -1;
+
+	CPU_ZERO(&new_mask);
+	CPU_SET(cpu, &new_mask);
+
+	err = sched_setaffinity(0, sizeof(new_mask), &new_mask);
+	if (!ASSERT_OK(err, "sched_setaffinity"))
+		return -1;
+
+	return 0;
+}
+
+static void test_percpu_hash_flags_combination(void)
+{
+	test_percpu_map_flags_combination(BPF_MAP_TYPE_PERCPU_HASH);
+}
+
+static void test_lru_percpu_hash_flags_combination(void)
+{
+	cpu_set_t old_mask;
+
+	if (pin_current_cpu(&old_mask))
+		return;
+
+	test_percpu_map_flags_combination(BPF_MAP_TYPE_LRU_PERCPU_HASH);
+
+	sched_setaffinity(0, sizeof(old_mask), &old_mask);
+}
+
+static void test_percpu_array_flags_combination(void)
+{
+	test_percpu_map_flags_combination(BPF_MAP_TYPE_PERCPU_ARRAY);
+}
+
 void test_percpu_alloc(void)
 {
 	if (test__start_subtest("array"))
@@ -565,4 +759,10 @@ void test_percpu_alloc(void)
 		test_array_cpu_flag();
 	if (test__start_subtest("cpu_flag_hash"))
 		test_hash_cpu_flag();
+	if (test__start_subtest("cpu_flag_combination_percpu_hash"))
+		test_percpu_hash_flags_combination();
+	if (test__start_subtest("cpu_flag_combination_lru_percpu_hash"))
+		test_lru_percpu_hash_flags_combination();
+	if (test__start_subtest("cpu_flag_combination_percpu_array"))
+		test_percpu_array_flags_combination();
 }
-- 
2.47.3

Re: [PATCH bpf v4 3/3] selftests/bpf: add tests for percpu map flags combination

[Leon Hwang]

On 4/10/26 19:10, Masoud Aghasi wrote:
> All possible combinations of (BPF_EXIST, BPF_NOEXIST) and
> (BPF_F_ALL_CPUS, BPF_F_CPU) flags are covered for all percpu map types.
> 
> As BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE does not support BPF_NOEXIST and
> also in order to reduce the amount of code duplicates, I added its
> new test scenarios to the existing cpu_flag_percpu_cgroup_storage test.
> 
> But for other percpu map types, I added new tests to be able to
> exercise all flag combinations and the edge cases such as percpu LRU
> unnecessary deletion issue.
> 
> Signed-off-by: Masoud Aghasi <maghasi@disroot.org>
> ---
>  .../selftests/bpf/prog_tests/percpu_alloc.c   | 200 ++++++++++++++++++
>  1 file changed, 200 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c b/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c
> index 7b4a1e24363b..1f33ea20d845 100644
> --- a/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c
> +++ b/tools/testing/selftests/bpf/prog_tests/percpu_alloc.c
> @@ -449,6 +449,48 @@ static void test_lru_percpu_hash_cpu_flag_create(void)
>  	test_percpu_map_cpu_flag_create(BPF_MAP_TYPE_LRU_PERCPU_HASH, 0);
>  }
>  
> +static void test_percpu_cgroup_storage_flags_combination(struct bpf_map *map, int nr_cpus,
> +							  struct bpf_cgroup_storage_key *key)
> +{
> +	int err;
> +	u64 flags = 0;
> +	size_t value_sz = sizeof(u32);
> +	size_t elem_sz = roundup(value_sz, 8);
> +	u32 *values = NULL;

Pls keep these lines in inverted Christmas tree style.

> +
> +	values = calloc(nr_cpus, elem_sz);
> +	if (!ASSERT_OK_PTR(values, "calloc values"))
> +		return;
> +
> +	flags = BPF_NOEXIST | BPF_EXIST;
> +	err = bpf_map__update_elem(map, key, sizeof(*key), values, elem_sz * nr_cpus, flags);
> +	if (!ASSERT_EQ(err, -EINVAL, "bpf_map__update_elem noexist|exist"))
> +		goto out;
> +
> +	flags = BPF_F_ALL_CPUS | BPF_NOEXIST;
> +	err = bpf_map__update_elem(map, key, sizeof(*key), values, value_sz, flags);
> +	if (!ASSERT_EQ(err, -EINVAL, "bpf_map__update_elem all_cpus|noexist"))
> +		goto out;
> +
> +	flags = BPF_F_CPU | BPF_NOEXIST;
> +	err = bpf_map__update_elem(map, key, sizeof(*key), values, value_sz, flags);
> +	if (!ASSERT_EQ(err, -EINVAL, "bpf_map__update_elem cpu|noexist"))
> +		goto out;
> +
> +	flags = BPF_F_ALL_CPUS | BPF_EXIST;
> +	err = bpf_map__update_elem(map, key, sizeof(*key), values, value_sz, flags);
> +	if (!ASSERT_OK(err, "bpf_map__update_elem all_cpus|exist"))
> +		goto out;
> +
> +	flags = BPF_F_CPU | BPF_EXIST;
> +	err = bpf_map__update_elem(map, key, sizeof(*key), values, value_sz, flags);
> +	if (!ASSERT_OK(err, "bpf_map__update_elem cpu|exist"))
> +		goto out;

This 'goto out' is unnecessary.

For these two bpf_map__update_elem() calls, better to set values before
updating, then to verify the values after updating.

> +
> +out:
> +	free(values);
> +}
> +
>  static void test_percpu_cgroup_storage_cpu_flag(void)
>  {
>  	struct percpu_alloc_array *skel = NULL;
> @@ -489,6 +531,7 @@ static void test_percpu_cgroup_storage_cpu_flag(void)
>  		goto out;
>  
>  	test_percpu_map_op_cpu_flag(map, &key, sizeof(key), 1, nr_cpus, false);
> +	test_percpu_cgroup_storage_flags_combination(map, nr_cpus, &key);
>  out:
>  	bpf_prog_detach2(-1, cgroup, BPF_CGROUP_INET_EGRESS);
>  	close(cgroup);
> @@ -537,6 +580,157 @@ static void test_hash_cpu_flag(void)
>  	test_map_op_cpu_flag(BPF_MAP_TYPE_HASH);
>  }
>  
> +static void test_percpu_map_flags_combination(enum bpf_map_type map_type)
> +{
> +	size_t value_sz = 8;
> +	void *values = NULL;
> +	u32 max_entries = 3, key = 0;
> +	u64 flags = 0;
> +	int err, map_fd, nr_cpus;
> +	bool is_hash_map = (map_type == BPF_MAP_TYPE_PERCPU_HASH ||
> +			    map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);

Ditto the style.

We can pass 'bool is_hash_map' via parameter.

> +
> +	nr_cpus = libbpf_num_possible_cpus();
> +	if (!ASSERT_GT(nr_cpus, 0, "libbpf_num_possible_cpus"))
> +		return;
> +
> +	values = calloc(nr_cpus, value_sz);
> +	if (!ASSERT_OK_PTR(values, "calloc values"))
> +		return;
> +
> +	map_fd = bpf_map_create(map_type, "test_flags_combination_map",
> +				sizeof(u32), value_sz, max_entries, NULL);
> +	if (!ASSERT_GE(map_fd, 0, "bpf_map_create")) {
> +		free(values);
> +		return;
> +	}
> +
> +	flags = BPF_NOEXIST | BPF_EXIST;
> +	err = bpf_map_update_elem(map_fd, &key, values, flags);
> +	if (!ASSERT_EQ(err, -EINVAL, "bpf_map_update_elem noexist|exist"))
> +		goto out;
> +
> +	flags = BPF_F_ALL_CPUS | BPF_NOEXIST;
> +	key = 0;
> +	err = bpf_map_update_elem(map_fd, &key, values, flags);
> +	if (is_hash_map) {
> +		if (!ASSERT_OK(err, "bpf_map_update_elem all_cpus|noexist"))
> +			goto out;
> +
> +		err = bpf_map_update_elem(map_fd, &key, values, flags);
> +		if (!ASSERT_EQ(err, -EEXIST, "bpf_map_update_elem all_cpus|noexist"))
> +			goto out;
> +	} else {
> +		if (!ASSERT_EQ(err, -EEXIST, "bpf_map_update_elem all_cpus|noexist"))
> +			goto out;
> +	}

The 'if (!ASSERT_EQ(err, ...))' can be moved after 'if (is_hash_map)'.

if (is_hash_map) {
	if (!ASSERT_EQ(err, ...))
		goto out;

	err = bpf_map_update_elem(...);
}
if (!ASSERT_EQ(err, ...))
	goto out;

> +
> +	flags = BPF_F_CPU | BPF_NOEXIST;
> +	key = 1;
> +	err = bpf_map_update_elem(map_fd, &key, values, flags);
> +	if (is_hash_map) {
> +		if (!ASSERT_OK(err, "bpf_map_update_elem cpu|noexist"))
> +			goto out;
> +
> +		err = bpf_map_update_elem(map_fd, &key, values, flags);
> +		if (!ASSERT_EQ(err, -EEXIST, "bpf_map_update_elem cpu|noexist"))
> +			goto out;
> +	} else {
> +		if (!ASSERT_EQ(err, -EEXIST, "bpf_map_update_elem cpu|noexist"))
> +			goto out;
> +	}
> +
> +	flags = BPF_F_ALL_CPUS | BPF_EXIST;
> +	key = 2;
> +	err = bpf_map_update_elem(map_fd, &key, values, flags);
> +	if (is_hash_map) {
> +		if (!ASSERT_EQ(err, -ENOENT, "bpf_map_update_elem all_cpus|exist"))
> +			goto out;
> +	} else {
> +		if (!ASSERT_OK(err, "bpf_map_update_elem all_cpus|exist"))
> +			goto out;
> +	}
> +
> +	flags = BPF_F_CPU | BPF_EXIST;
> +	err = bpf_map_update_elem(map_fd, &key, values, flags);
> +	if (is_hash_map) {
> +		if (!ASSERT_EQ(err, -ENOENT, "bpf_map_update_elem cpu|exist"))
> +			goto out;
> +	} else {
> +		if (!ASSERT_OK(err, "bpf_map_update_elem cpu|exist"))
> +			goto out;
> +	}
> +
> +	if (map_type != BPF_MAP_TYPE_LRU_PERCPU_HASH)
> +		goto out;
> +
> +	/* Percpu LRU hash map should not delete old entries unnecessarily */
> +	flags = BPF_F_ALL_CPUS | BPF_NOEXIST;
> +	key = 2;
> +	err = bpf_map_update_elem(map_fd, &key, values, flags);
> +	if (!ASSERT_OK(err, "bpf_map_update_elem unnecessary_deletion"))
> +		goto out;
> +
> +	flags = BPF_F_ALL_CPUS | BPF_EXIST;
> +	err = bpf_map_update_elem(map_fd, &key, values, flags);
> +	if (!ASSERT_OK(err, "bpf_map_update_elem unnecessary_deletion"))
> +		goto out;
> +
> +	key = 0;
> +	err = bpf_map_lookup_elem(map_fd, &key, values);
> +	if (!ASSERT_OK(err, "bpf_map_lookup_elem unnecessary_deletion"))
> +		goto out;

This 'goto' is unnecessary.

> +
> +out:
> +	close(map_fd);
> +	free(values);
> +}

After reading test_percpu_map_flags_combination(), two helpers are
needed to verify the updated values. One for updating with BPF_F_CPU,
another one for updating with BPF_F_ALL_CPUS.

Thanks,
Leon

> [...]

Re: [PATCH bpf v4 3/3] selftests/bpf: add tests for percpu map flags combination

[Masoud Aghasi]

On 05/10/2026 04:12, Leon Hwang wrote:
> On 4/10/26 19:10, Masoud Aghasi wrote:

[...]

>> +{
>> +	int err;
>> +	u64 flags = 0;
>> +	size_t value_sz = sizeof(u32);
>> +	size_t elem_sz = roundup(value_sz, 8);
>> +	u32 *values = NULL;
> 
> Pls keep these lines in inverted Christmas tree style.
> 

[...]

>> +	flags = BPF_F_CPU | BPF_EXIST;
>> +	err = bpf_map__update_elem(map, key, sizeof(*key), values, value_sz, flags);
>> +	if (!ASSERT_OK(err, "bpf_map__update_elem cpu|exist"))
>> +		goto out;
> 
> This 'goto out' is unnecessary.
> 
> For these two bpf_map__update_elem() calls, better to set values before
> updating, then to verify the values after updating.
> 

[...]

>> +static void test_percpu_map_flags_combination(enum bpf_map_type map_type)
>> +{
>> +	size_t value_sz = 8;
>> +	void *values = NULL;
>> +	u32 max_entries = 3, key = 0;
>> +	u64 flags = 0;
>> +	int err, map_fd, nr_cpus;
>> +	bool is_hash_map = (map_type == BPF_MAP_TYPE_PERCPU_HASH ||
>> +			    map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
> 
> Ditto the style.
> 
> We can pass 'bool is_hash_map' via parameter.
> 

[...]

>> +	flags = BPF_F_ALL_CPUS | BPF_NOEXIST;
>> +	key = 0;
>> +	err = bpf_map_update_elem(map_fd, &key, values, flags);
>> +	if (is_hash_map) {
>> +		if (!ASSERT_OK(err, "bpf_map_update_elem all_cpus|noexist"))
>> +			goto out;
>> +
>> +		err = bpf_map_update_elem(map_fd, &key, values, flags);
>> +		if (!ASSERT_EQ(err, -EEXIST, "bpf_map_update_elem all_cpus|noexist"))
>> +			goto out;
>> +	} else {
>> +		if (!ASSERT_EQ(err, -EEXIST, "bpf_map_update_elem all_cpus|noexist"))
>> +			goto out;
>> +	}
> 
> The 'if (!ASSERT_EQ(err, ...))' can be moved after 'if (is_hash_map)'.
> 
> if (is_hash_map) {
> 	if (!ASSERT_EQ(err, ...))
> 		goto out;
> 
> 	err = bpf_map_update_elem(...);
> }
> if (!ASSERT_EQ(err, ...))
> 	goto out;
> 

[...]

>> +	key = 0;
>> +	err = bpf_map_lookup_elem(map_fd, &key, values);
>> +	if (!ASSERT_OK(err, "bpf_map_lookup_elem unnecessary_deletion"))
>> +		goto out;
> 
> This 'goto' is unnecessary.
> 
>> +
>> +out:
>> +	close(map_fd);
>> +	free(values);
>> +}
> 
> After reading test_percpu_map_flags_combination(), two helpers are
> needed to verify the updated values. One for updating with BPF_F_CPU,
> another one for updating with BPF_F_ALL_CPUS.
> 
> Thanks,
> Leon

Thanks, I will apply your comments to the v5.
just regarding the is_hash_map, isn't it better to keep it as an
implementation detail inside the function and avoid introducing an
unnecessary invariant for callers to maintain?

Re: [PATCH bpf v4 3/3] selftests/bpf: add tests for percpu map flags combination

[Leon Hwang]

On 5/10/26 23:19, Masoud Aghasi wrote:
> On 05/10/2026 04:12, Leon Hwang wrote:
>> On 4/10/26 19:10, Masoud Aghasi wrote:

[...]

>>
>> After reading test_percpu_map_flags_combination(), two helpers are
>> needed to verify the updated values. One for updating with BPF_F_CPU,
>> another one for updating with BPF_F_ALL_CPUS.
>>
>> Thanks,
>> Leon
> 
> Thanks, I will apply your comments to the v5.
> just regarding the is_hash_map, isn't it better to keep it as an
> implementation detail inside the function and avoid introducing an
> unnecessary invariant for callers to maintain?

I think either way is fine in this selftest.

Thanks,
Leon