[PATCH bpf v1 0/2] bpf: cpumap: fix error propagation in

[PATCH bpf v1 0/2] bpf: cpumap: fix error propagation in

[Kohei Enju]

This series fixes incorrect error propagation in cpumap and adds
selftests that cover the failure cases.

Currently, failures returned from __cpu_map_entry_alloc() are ignored
and always converted to -ENOMEM by cpu_map_update_elem(). This series
ensures the correct error propagation and adds selftests.

Kohei Enju (2):
  bpf: cpumap: propagate underlying error in cpu_map_update_elem()
  selftests/bpf: add tests for attaching invalid fd

 kernel/bpf/cpumap.c                           | 21 ++++++++++++-------
 .../bpf/prog_tests/xdp_cpumap_attach.c        | 19 +++++++++++++++--
 2 files changed, 30 insertions(+), 10 deletions(-)

-- 
2.51.0

[PATCH bpf v1 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

[Kohei Enju]

After commit 9216477449f3 ("bpf: cpumap: Add the possibility to attach
an eBPF program to cpumap"), __cpu_map_entry_alloc() may fail with
errors other than -ENOMEM, such as -EBADF or -EINVAL.

However, __cpu_map_entry_alloc() returns NULL on all failures, and
cpu_map_update_elem() unconditionally converts this NULL into -ENOMEM.
As a result, user space always receives -ENOMEM regardless of the actual
underlying error.

Examples of unexpected behavior:
  - Nonexistent fd  : -ENOMEM (should be -EBADF)
  - Non-BPF fd      : -ENOMEM (should be -EINVAL)
  - Bad attach type : -ENOMEM (should be -EINVAL)

Change __cpu_map_entry_alloc() to return ERR_PTR(err) instead of NULL
and have cpu_map_update_elem() propagate this error.

Fixes: 9216477449f3 ("bpf: cpumap: Add the possibility to attach an eBPF program to cpumap")
Signed-off-by: Kohei Enju <enjuk@amazon.com>
---
 kernel/bpf/cpumap.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 703e5df1f4ef..04171fbc39cb 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -430,7 +430,7 @@ static struct bpf_cpu_map_entry *
 __cpu_map_entry_alloc(struct bpf_map *map, struct bpf_cpumap_val *value,
 		      u32 cpu)
 {
-	int numa, err, i, fd = value->bpf_prog.fd;
+	int numa, err = -ENOMEM, i, fd = value->bpf_prog.fd;
 	gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
 	struct bpf_cpu_map_entry *rcpu;
 	struct xdp_bulk_queue *bq;
@@ -440,7 +440,7 @@ __cpu_map_entry_alloc(struct bpf_map *map, struct bpf_cpumap_val *value,
 
 	rcpu = bpf_map_kmalloc_node(map, sizeof(*rcpu), gfp | __GFP_ZERO, numa);
 	if (!rcpu)
-		return NULL;
+		return ERR_PTR(err);
 
 	/* Alloc percpu bulkq */
 	rcpu->bulkq = bpf_map_alloc_percpu(map, sizeof(*rcpu->bulkq),
@@ -468,16 +468,21 @@ __cpu_map_entry_alloc(struct bpf_map *map, struct bpf_cpumap_val *value,
 	rcpu->value.qsize  = value->qsize;
 	gro_init(&rcpu->gro);
 
-	if (fd > 0 && __cpu_map_load_bpf_program(rcpu, map, fd))
-		goto free_ptr_ring;
+	if (fd > 0) {
+		err = __cpu_map_load_bpf_program(rcpu, map, fd);
+		if (err)
+			goto free_ptr_ring;
+	}
 
 	/* Setup kthread */
 	init_completion(&rcpu->kthread_running);
 	rcpu->kthread = kthread_create_on_node(cpu_map_kthread_run, rcpu, numa,
 					       "cpumap/%d/map:%d", cpu,
 					       map->id);
-	if (IS_ERR(rcpu->kthread))
+	if (IS_ERR(rcpu->kthread)) {
+		err = PTR_ERR(rcpu->kthread);
 		goto free_prog;
+	}
 
 	/* Make sure kthread runs on a single CPU */
 	kthread_bind(rcpu->kthread, cpu);
@@ -503,7 +508,7 @@ __cpu_map_entry_alloc(struct bpf_map *map, struct bpf_cpumap_val *value,
 	free_percpu(rcpu->bulkq);
 free_rcu:
 	kfree(rcpu);
-	return NULL;
+	return ERR_PTR(err);
 }
 
 static void __cpu_map_entry_free(struct work_struct *work)
@@ -596,8 +601,8 @@ static long cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
 	} else {
 		/* Updating qsize cause re-allocation of bpf_cpu_map_entry */
 		rcpu = __cpu_map_entry_alloc(map, &cpumap_value, key_cpu);
-		if (!rcpu)
-			return -ENOMEM;
+		if (IS_ERR(rcpu))
+			return PTR_ERR(rcpu);
 	}
 	rcu_read_lock();
 	__cpu_map_entry_replace(cmap, key_cpu, rcpu);
-- 
2.51.0

Re: [PATCH bpf v1 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

[Alexei Starovoitov]

On Fri, Nov 28, 2025 at 8:05 AM Kohei Enju <enjuk@amazon.com> wrote:
>
> After commit 9216477449f3 ("bpf: cpumap: Add the possibility to attach
> an eBPF program to cpumap"), __cpu_map_entry_alloc() may fail with
> errors other than -ENOMEM, such as -EBADF or -EINVAL.
>
> However, __cpu_map_entry_alloc() returns NULL on all failures, and
> cpu_map_update_elem() unconditionally converts this NULL into -ENOMEM.
> As a result, user space always receives -ENOMEM regardless of the actual
> underlying error.
>
> Examples of unexpected behavior:
>   - Nonexistent fd  : -ENOMEM (should be -EBADF)
>   - Non-BPF fd      : -ENOMEM (should be -EINVAL)
>   - Bad attach type : -ENOMEM (should be -EINVAL)
>
> Change __cpu_map_entry_alloc() to return ERR_PTR(err) instead of NULL
> and have cpu_map_update_elem() propagate this error.
>
> Fixes: 9216477449f3 ("bpf: cpumap: Add the possibility to attach an eBPF program to cpumap")

The current behavior is what it is. It's not a bug and
this patch is not a fix. It's probably an ok improvement,
but since it changes user visible behavior we have to be careful.

I'd like Jesper and/or other cpumap experts to confirm that it's ok.

Re: [PATCH bpf v1 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

[Kohei Enju]

On Tue, 2 Dec 2025 17:08:32 -0800, Alexei Starovoitov wrote:

>On Fri, Nov 28, 2025 at 8:05 AM Kohei Enju <enjuk@amazon.com> wrote:
>>
>> After commit 9216477449f3 ("bpf: cpumap: Add the possibility to attach
>> an eBPF program to cpumap"), __cpu_map_entry_alloc() may fail with
>> errors other than -ENOMEM, such as -EBADF or -EINVAL.
>>
>> However, __cpu_map_entry_alloc() returns NULL on all failures, and
>> cpu_map_update_elem() unconditionally converts this NULL into -ENOMEM.
>> As a result, user space always receives -ENOMEM regardless of the actual
>> underlying error.
>>
>> Examples of unexpected behavior:
>>   - Nonexistent fd  : -ENOMEM (should be -EBADF)
>>   - Non-BPF fd      : -ENOMEM (should be -EINVAL)
>>   - Bad attach type : -ENOMEM (should be -EINVAL)
>>
>> Change __cpu_map_entry_alloc() to return ERR_PTR(err) instead of NULL
>> and have cpu_map_update_elem() propagate this error.
>>
>> Fixes: 9216477449f3 ("bpf: cpumap: Add the possibility to attach an eBPF program to cpumap")
>
>The current behavior is what it is. It's not a bug and
>this patch is not a fix. It's probably an ok improvement,
>but since it changes user visible behavior we have to be careful.

Oops, got it.
When I resend, I'll remove the tag and send to bpf-next, not to bpf.

Thank you for taking a look.

>
>I'd like Jesper and/or other cpumap experts to confirm that it's ok.
>

Sure, I'd like to wait for reactions from cpumap experts.

Re: [PATCH bpf v1 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

[Jesper Dangaard Brouer]

On 03/12/2025 11.40, Kohei Enju wrote:
> On Tue, 2 Dec 2025 17:08:32 -0800, Alexei Starovoitov wrote:
> 
>> On Fri, Nov 28, 2025 at 8:05 AM Kohei Enju <enjuk@amazon.com> wrote:
>>>
>>> After commit 9216477449f3 ("bpf: cpumap: Add the possibility to attach
>>> an eBPF program to cpumap"), __cpu_map_entry_alloc() may fail with
>>> errors other than -ENOMEM, such as -EBADF or -EINVAL.
>>>
>>> However, __cpu_map_entry_alloc() returns NULL on all failures, and
>>> cpu_map_update_elem() unconditionally converts this NULL into -ENOMEM.
>>> As a result, user space always receives -ENOMEM regardless of the actual
>>> underlying error.
>>>
>>> Examples of unexpected behavior:
>>>    - Nonexistent fd  : -ENOMEM (should be -EBADF)
>>>    - Non-BPF fd      : -ENOMEM (should be -EINVAL)
>>>    - Bad attach type : -ENOMEM (should be -EINVAL)
>>>
>>> Change __cpu_map_entry_alloc() to return ERR_PTR(err) instead of NULL
>>> and have cpu_map_update_elem() propagate this error.
>>>
>>> Fixes: 9216477449f3 ("bpf: cpumap: Add the possibility to attach an eBPF program to cpumap")
>>
>> The current behavior is what it is. It's not a bug and
>> this patch is not a fix. It's probably an ok improvement,
>> but since it changes user visible behavior we have to be careful.
> 
> Oops, got it.
> When I resend, I'll remove the tag and send to bpf-next, not to bpf.
> 
> Thank you for taking a look.
> 
>>
>> I'd like Jesper and/or other cpumap experts to confirm that it's ok.
>>
> 
> Sure, I'd like to wait for reactions from cpumap experts.

Skimmed the code changes[1] and they look good to me :-)

Bcc'ed some Cloudflare people that use cpumap, so add link to change:
  [1] https://lore.kernel.org/all/20251128160504.57844-2-enjuk@amazon.com/
  ... if they want to object

--Jesper

Re: [PATCH bpf v1 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

[Toke Høiland-Jørgensen]

Jesper Dangaard Brouer <hawk@kernel.org> writes:

> On 03/12/2025 11.40, Kohei Enju wrote:
>> On Tue, 2 Dec 2025 17:08:32 -0800, Alexei Starovoitov wrote:
>> 
>>> On Fri, Nov 28, 2025 at 8:05 AM Kohei Enju <enjuk@amazon.com> wrote:
>>>>
>>>> After commit 9216477449f3 ("bpf: cpumap: Add the possibility to attach
>>>> an eBPF program to cpumap"), __cpu_map_entry_alloc() may fail with
>>>> errors other than -ENOMEM, such as -EBADF or -EINVAL.
>>>>
>>>> However, __cpu_map_entry_alloc() returns NULL on all failures, and
>>>> cpu_map_update_elem() unconditionally converts this NULL into -ENOMEM.
>>>> As a result, user space always receives -ENOMEM regardless of the actual
>>>> underlying error.
>>>>
>>>> Examples of unexpected behavior:
>>>>    - Nonexistent fd  : -ENOMEM (should be -EBADF)
>>>>    - Non-BPF fd      : -ENOMEM (should be -EINVAL)
>>>>    - Bad attach type : -ENOMEM (should be -EINVAL)
>>>>
>>>> Change __cpu_map_entry_alloc() to return ERR_PTR(err) instead of NULL
>>>> and have cpu_map_update_elem() propagate this error.
>>>>
>>>> Fixes: 9216477449f3 ("bpf: cpumap: Add the possibility to attach an eBPF program to cpumap")
>>>
>>> The current behavior is what it is. It's not a bug and
>>> this patch is not a fix. It's probably an ok improvement,
>>> but since it changes user visible behavior we have to be careful.
>> 
>> Oops, got it.
>> When I resend, I'll remove the tag and send to bpf-next, not to bpf.
>> 
>> Thank you for taking a look.
>> 
>>>
>>> I'd like Jesper and/or other cpumap experts to confirm that it's ok.
>>>
>> 
>> Sure, I'd like to wait for reactions from cpumap experts.
>
> Skimmed the code changes[1] and they look good to me :-)

We have one example of a use of the cpumap programs in xdp-tools, and
there we just report the error message to the user. I would guess other
apps would follow the same pattern rather than react to a specific error
code; especially since there's only one error code being used here.

So I agree, this should be OK to change.

-Toke

Re: [PATCH bpf v1 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

[Kohei Enju]

On Wed, 03 Dec 2025 13:31:29 +0100, Toke Høiland-Jørgensen wrote:

>Jesper Dangaard Brouer <hawk@kernel.org> writes:
>
>> On 03/12/2025 11.40, Kohei Enju wrote:
>>> On Tue, 2 Dec 2025 17:08:32 -0800, Alexei Starovoitov wrote:
>>> 
>>>> On Fri, Nov 28, 2025 at 8:05 AM Kohei Enju <enjuk@amazon.com> wrote:
>>>>>
>>>>> After commit 9216477449f3 ("bpf: cpumap: Add the possibility to attach
>>>>> an eBPF program to cpumap"), __cpu_map_entry_alloc() may fail with
>>>>> errors other than -ENOMEM, such as -EBADF or -EINVAL.
>>>>>
>>>>> However, __cpu_map_entry_alloc() returns NULL on all failures, and
>>>>> cpu_map_update_elem() unconditionally converts this NULL into -ENOMEM.
>>>>> As a result, user space always receives -ENOMEM regardless of the actual
>>>>> underlying error.
>>>>>
>>>>> Examples of unexpected behavior:
>>>>>    - Nonexistent fd  : -ENOMEM (should be -EBADF)
>>>>>    - Non-BPF fd      : -ENOMEM (should be -EINVAL)
>>>>>    - Bad attach type : -ENOMEM (should be -EINVAL)
>>>>>
>>>>> Change __cpu_map_entry_alloc() to return ERR_PTR(err) instead of NULL
>>>>> and have cpu_map_update_elem() propagate this error.
>>>>>
>>>>> Fixes: 9216477449f3 ("bpf: cpumap: Add the possibility to attach an eBPF program to cpumap")
>>>>
>>>> The current behavior is what it is. It's not a bug and
>>>> this patch is not a fix. It's probably an ok improvement,
>>>> but since it changes user visible behavior we have to be careful.
>>> 
>>> Oops, got it.
>>> When I resend, I'll remove the tag and send to bpf-next, not to bpf.
>>> 
>>> Thank you for taking a look.
>>> 
>>>>
>>>> I'd like Jesper and/or other cpumap experts to confirm that it's ok.
>>>>
>>> 
>>> Sure, I'd like to wait for reactions from cpumap experts.
>>
>> Skimmed the code changes[1] and they look good to me :-)
>
>We have one example of a use of the cpumap programs in xdp-tools, and
>there we just report the error message to the user. I would guess other
>apps would follow the same pattern rather than react to a specific error
>code; especially since there's only one error code being used here.
>
>So I agree, this should be OK to change.
>
>-Toke

Thank you for the clarification, Toke and Jesper.
Since I see no objections so far, I'll work on v2 and resend next week.

Re: [PATCH bpf v1 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

[Kohei Enju]

On Sat, 6 Dec 2025 16:29:44 +0900, Kohei Enju wrote:

>On Wed, 03 Dec 2025 13:31:29 +0100, Toke H�iland-J�rgensen wrote:
>
>>Jesper Dangaard Brouer <hawk@kernel.org> writes:
>>
>>> On 03/12/2025 11.40, Kohei Enju wrote:
>>>> On Tue, 2 Dec 2025 17:08:32 -0800, Alexei Starovoitov wrote:
>>>> 
>>>>> On Fri, Nov 28, 2025 at 8:05\u202fAM Kohei Enju <enjuk@amazon.com> wrote:
>>>>>>
>>>>>> After commit 9216477449f3 ("bpf: cpumap: Add the possibility to attach
>>>>>> an eBPF program to cpumap"), __cpu_map_entry_alloc() may fail with
>>>>>> errors other than -ENOMEM, such as -EBADF or -EINVAL.
>>>>>>
>>>>>> However, __cpu_map_entry_alloc() returns NULL on all failures, and
>>>>>> cpu_map_update_elem() unconditionally converts this NULL into -ENOMEM.
>>>>>> As a result, user space always receives -ENOMEM regardless of the actual
>>>>>> underlying error.
>>>>>>
>>>>>> Examples of unexpected behavior:
>>>>>>    - Nonexistent fd  : -ENOMEM (should be -EBADF)
>>>>>>    - Non-BPF fd      : -ENOMEM (should be -EINVAL)
>>>>>>    - Bad attach type : -ENOMEM (should be -EINVAL)
>>>>>>
>>>>>> Change __cpu_map_entry_alloc() to return ERR_PTR(err) instead of NULL
>>>>>> and have cpu_map_update_elem() propagate this error.
>>>>>>
>>>>>> Fixes: 9216477449f3 ("bpf: cpumap: Add the possibility to attach an eBPF program to cpumap")
>>>>>
>>>>> The current behavior is what it is. It's not a bug and
>>>>> this patch is not a fix. It's probably an ok improvement,
>>>>> but since it changes user visible behavior we have to be careful.
>>>> 
>>>> Oops, got it.
>>>> When I resend, I'll remove the tag and send to bpf-next, not to bpf.
>>>> 
>>>> Thank you for taking a look.
>>>> 
>>>>>
>>>>> I'd like Jesper and/or other cpumap experts to confirm that it's ok.
>>>>>
>>>> 
>>>> Sure, I'd like to wait for reactions from cpumap experts.
>>>
>>> Skimmed the code changes[1] and they look good to me :-)
>>
>>We have one example of a use of the cpumap programs in xdp-tools, and
>>there we just report the error message to the user. I would guess other
>>apps would follow the same pattern rather than react to a specific error
>>code; especially since there's only one error code being used here.
>>
>>So I agree, this should be OK to change.
>>
>>-Toke
>
>Thank you for the clarification, Toke and Jesper.
>Since I see no objections so far, I'll work on v2 and resend next week.

Ah, I forgot that bpf-next is closed until Jan 2nd due to the merge window.
I'll resend v2 after Jan 2nd :)

Re: [PATCH bpf v1 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

[Alexei Starovoitov]

On Sat, Dec 6, 2025 at 9:01 PM Kohei Enju <enjuk@amazon.com> wrote:
>
> Ah, I forgot that bpf-next is closed until Jan 2nd due to the merge window.
> I'll resend v2 after Jan 2nd :)

?! It's not closed. net-next is.

Re: [PATCH bpf v1 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

[Kohei Enju]

On Sat, 6 Dec 2025 04:06:38 -0800, Alexei Starovoitov wrote:

>On Sat, Dec 6, 2025 at 9:01 PM Kohei Enju <enjuk@amazon.com> wrote:
>>
>> Ah, I forgot that bpf-next is closed until Jan 2nd due to the merge window.
>> I'll resend v2 after Jan 2nd :)
>
>?! It's not closed. net-next is.

Oh, really?
Hmm, I've read the documentation[1], but I may misunderstand something. Perhaps that documentation is outdated?

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/bpf/bpf_devel_QA.rst#n232

Re: [PATCH bpf v1 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

[Alexei Starovoitov]

On Sat, Dec 6, 2025 at 9:14 PM Kohei Enju <enjuk@amazon.com> wrote:
>
> On Sat, 6 Dec 2025 04:06:38 -0800, Alexei Starovoitov wrote:
>
> >On Sat, Dec 6, 2025 at 9:01 PM Kohei Enju <enjuk@amazon.com> wrote:
> >>
> >> Ah, I forgot that bpf-next is closed until Jan 2nd due to the merge window.
> >> I'll resend v2 after Jan 2nd :)
> >
> >?! It's not closed. net-next is.
>
> Oh, really?
> Hmm, I've read the documentation[1], but I may misunderstand something. Perhaps that documentation is outdated?
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/bpf/bpf_devel_QA.rst#n232

yes. It's seriously outdated. bpf-next was never closed.

Re: [PATCH bpf v1 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

[Kohei Enju]

On Sat, 6 Dec 2025 04:22:02 -0800, Alexei Starovoitov wrote:

>On Sat, Dec 6, 2025 at 9:14 PM Kohei Enju <enjuk@amazon.com> wrote:
>>
>> On Sat, 6 Dec 2025 04:06:38 -0800, Alexei Starovoitov wrote:
>>
>> >On Sat, Dec 6, 2025 at 9:01 PM Kohei Enju <enjuk@amazon.com> wrote:
>> >>
>> >> Ah, I forgot that bpf-next is closed until Jan 2nd due to the merge window.
>> >> I'll resend v2 after Jan 2nd :)
>> >
>> >?! It's not closed. net-next is.
>>
>> Oh, really?
>> Hmm, I've read the documentation[1], but I may misunderstand something. Perhaps that documentation is outdated?
>>
>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/bpf/bpf_devel_QA.rst#n232
>
>yes. It's seriously outdated. bpf-next was never closed.

Today I learned! Thank you for the clarification.

As originally planned, I will work on v2 next week :)

[PATCH bpf v1 2/2] selftests/bpf: add tests for attaching invalid fd

[Kohei Enju]

Add test cases for situations where adding the following types of file
descriptors to a cpumap entry should fail:
- Non-BPF file descriptor (expect -EINVAL)
- Nonexistent file descriptor (expect -EBADF)

Also tighten the assertion for the expected error when adding a
non-BPF_XDP_CPUMAP program to a cpumap entry.

Signed-off-by: Kohei Enju <enjuk@amazon.com>
---
 .../bpf/prog_tests/xdp_cpumap_attach.c        | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
index df27535995af..ad56e4370ce3 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
@@ -18,7 +18,7 @@ static void test_xdp_with_cpumap_helpers(void)
 	struct bpf_cpumap_val val = {
 		.qsize = 192,
 	};
-	int err, prog_fd, prog_redir_fd, map_fd;
+	int err, prog_fd, prog_redir_fd, map_fd, bad_fd;
 	struct nstoken *nstoken = NULL;
 	__u32 idx = 0;
 
@@ -79,7 +79,22 @@ static void test_xdp_with_cpumap_helpers(void)
 	val.qsize = 192;
 	val.bpf_prog.fd = bpf_program__fd(skel->progs.xdp_dummy_prog);
 	err = bpf_map_update_elem(map_fd, &idx, &val, 0);
-	ASSERT_NEQ(err, 0, "Add non-BPF_XDP_CPUMAP program to cpumap entry");
+	ASSERT_EQ(err, -EINVAL, "Add non-BPF_XDP_CPUMAP program to cpumap entry");
+
+	/* Try to attach non-BPF file descriptor */
+	bad_fd = open("/dev/null", O_RDONLY);
+	ASSERT_GE(bad_fd, 0, "Open /dev/null for non-BPF fd");
+
+	val.bpf_prog.fd = bad_fd;
+	err = bpf_map_update_elem(map_fd, &idx, &val, 0);
+	ASSERT_EQ(err, -EINVAL, "Add non-BPF fd to cpumap entry");
+
+	/* Try to attach nonexistent file descriptor */
+	err = close(bad_fd);
+	ASSERT_EQ(err, 0, "Close non-BPF fd for nonexistent fd");
+
+	err = bpf_map_update_elem(map_fd, &idx, &val, 0);
+	ASSERT_EQ(err, -EBADF, "Add nonexistent fd to cpumap entry");
 
 	/* Try to attach BPF_XDP program with frags to cpumap when we have
 	 * already loaded a BPF_XDP program on the map
-- 
2.51.0