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bpf: check max_entries before allocating memory

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For maps of type BPF_MAP_TYPE_CPUMAP memory is allocated first before
checking the max_entries argument. If then max_entries is greater than
NR_CPUS additional work needs to be done to free allocated memory before
an error is returned.
This changes moves the check on max_entries before the allocation
happens.

Signed-off-by: Florian Lehner <dev@der-flo.net>
Link: https://lore.kernel.org/r/20221028183405.59554-1-dev@der-flo.net
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
Florian Lehner 2022-10-28 20:34:05 +02:00 committed by Martin KaFai Lau
parent b6d207999c
commit e39e739ab5
1 changed files with 8 additions and 12 deletions
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20
kernel/bpf/cpumap.c
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@ -85,7 +85,6 @@ static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
{
u32 value_size = attr->value_size;
struct bpf_cpu_map *cmap;
int err = -ENOMEM;
if (!bpf_capable())
return ERR_PTR(-EPERM);
@ -97,29 +96,26 @@ static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
attr->map_flags & ~BPF_F_NUMA_NODE)
return ERR_PTR(-EINVAL);
/* Pre-limit array size based on NR_CPUS, not final CPU check */
if (attr->max_entries > NR_CPUS)
return ERR_PTR(-E2BIG);
cmap = bpf_map_area_alloc(sizeof(*cmap), NUMA_NO_NODE);
if (!cmap)
return ERR_PTR(-ENOMEM);
bpf_map_init_from_attr(&cmap->map, attr);
/* Pre-limit array size based on NR_CPUS, not final CPU check */
if (cmap->map.max_entries > NR_CPUS) {
err = -E2BIG;
goto free_cmap;
}
/* Alloc array for possible remote "destination" CPUs */
cmap->cpu_map = bpf_map_area_alloc(cmap->map.max_entries *
sizeof(struct bpf_cpu_map_entry *),
cmap->map.numa_node);
if (!cmap->cpu_map)
goto free_cmap;
if (!cmap->cpu_map) {
bpf_map_area_free(cmap);
return ERR_PTR(-ENOMEM);
}
return &cmap->map;
free_cmap:
bpf_map_area_free(cmap);
return ERR_PTR(err);
}
static void get_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)