Commit cf6eeb8f authored by Hou Tao's avatar Hou Tao Committed by Daniel Borkmann
Browse files

bpf: Remove unnecessary ring buffer size check 



The theoretical maximum size of ring buffer is about 64GB, but now the
size of ring buffer is specified by max_entries in bpf_attr and its
maximum value is (4GB - 1), and it won't be possible for overflow.

So just remove the unnecessary size check in ringbuf_map_alloc() but
keep the comments for possible extension in future.

Reported-by: default avatarDan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: default avatarHou Tao <houtao1@huawei.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Closes: https://lore.kernel.org/bpf/9c636a63-1f3d-442d-9223-96c2dccb9469@moroto.mountain
Link: https://lore.kernel.org/bpf/20230704074014.216616-1-houtao@huaweicloud.com
parent c20f9cef

kernel/bpf/ringbuf.c

+11 −15
Original line number Diff line number Diff line
@@ -23,15 +23,6 @@ 


#define RINGBUF_MAX_RECORD_SZ (UINT_MAX/4)



/* Maximum size of ring buffer area is limited by 32-bit page offset within

 * record header, counted in pages. Reserve 8 bits for extensibility, and take

 * into account few extra pages for consumer/producer pages and

 * non-mmap()'able parts. This gives 64GB limit, which seems plenty for single

 * ring buffer.

 */

#define RINGBUF_MAX_DATA_SZ \

	(((1ULL << 24) - RINGBUF_POS_PAGES - RINGBUF_PGOFF) * PAGE_SIZE)



struct bpf_ringbuf {

	wait_queue_head_t waitq;

	struct irq_work work;
@@ -161,6 +152,17 @@ static void bpf_ringbuf_notify(struct irq_work *work) 
	wake_up_all(&rb->waitq);

}



/* Maximum size of ring buffer area is limited by 32-bit page offset within

 * record header, counted in pages. Reserve 8 bits for extensibility, and

 * take into account few extra pages for consumer/producer pages and

 * non-mmap()'able parts, the current maximum size would be:

 *

 *     (((1ULL << 24) - RINGBUF_POS_PAGES - RINGBUF_PGOFF) * PAGE_SIZE)

 *

 * This gives 64GB limit, which seems plenty for single ring buffer. Now

 * considering that the maximum value of data_sz is (4GB - 1), there

 * will be no overflow, so just note the size limit in the comments.

 */

static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)

{

	struct bpf_ringbuf *rb;
@@ -193,12 +195,6 @@ static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr) 
	    !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 = bpf_map_area_alloc(sizeof(*rb_map), NUMA_NO_NODE);

	if (!rb_map)

		return ERR_PTR(-ENOMEM);