bpf: Enforce BPF ringbuf size to be the power of 2 (517bbe19) · Commits · 戴 / test

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: ("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

kernel/bpf/ringbuf.c

+8 −10

Original line number	Diff line number	Diff line
		@@ -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);

Admin message