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bpf: cpumap: propagate underlying error in cpu_map_update_elem()

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After commit 9216477449 ("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.

Signed-off-by: Kohei Enju <enjuk@amazon.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20251208131449.73036-2-enjuk@amazon.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kohei Enju
2025-12-08 22:14:31 +09:00
committed by Alexei Starovoitov
parent 5d9fb42f05
commit 48e11bad9a
1 changed files with 13 additions and 8 deletions
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21
kernel/bpf/cpumap.c
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@@ -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 @@ free_bulkq:
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);