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bpf: Enforce BPF ringbuf size to be the power of 2

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BPF ringbuf assumes the size to be a multiple of page size and the power of
2 value. The latter is important to avoid division while calculating position
inside the ring buffer and using (N-1) mask instead. This patch fixes omission
to enforce power-of-2 size rule.

Fixes: 457f44363a ("bpf: Implement BPF ring buffer and verifier support for it")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200630061500.1804799-1-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-06-29 23:15:00 -07:00 committed by Daniel Borkmann
parent 7e0245753f
commit 517bbe1994
1 changed files with 8 additions and 10 deletions
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18
kernel/bpf/ringbuf.c
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@ -132,15 +132,6 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
{
struct bpf_ringbuf *rb;
if (!data_sz || !PAGE_ALIGNED(data_sz))
return ERR_PTR(-EINVAL);
#ifdef CONFIG_64BIT
/* on 32-bit arch, it's impossible to overflow record's hdr->pgoff */
if (data_sz > RINGBUF_MAX_DATA_SZ)
return ERR_PTR(-E2BIG);
#endif
rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
if (!rb)
return ERR_PTR(-ENOMEM);
@ -166,9 +157,16 @@ static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
return ERR_PTR(-EINVAL);
if (attr->key_size || attr->value_size ||
attr->max_entries == 0 || !PAGE_ALIGNED(attr->max_entries))
!is_power_of_2(attr->max_entries) ||
!PAGE_ALIGNED(attr->max_entries))
return ERR_PTR(-EINVAL);
#ifdef CONFIG_64BIT
/* on 32-bit arch, it's impossible to overflow record's hdr->pgoff */
if (attr->max_entries > RINGBUF_MAX_DATA_SZ)
return ERR_PTR(-E2BIG);
#endif
rb_map = kzalloc(sizeof(*rb_map), GFP_USER);
if (!rb_map)
return ERR_PTR(-ENOMEM);