From: Hou Tao <houtao1@xxxxxxxxxx> 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: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Closes: https://lore.kernel.org/bpf/9c636a63-1f3d-442d-9223-96c2dccb9469@moroto.mountain Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx> --- kernel/bpf/ringbuf.c | 26 +++++++++++--------------- 1 file changed, 11 insertions(+), 15 deletions(-) diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c index 875ac9b698d9..f045fde632e5 100644 --- a/kernel/bpf/ringbuf.c +++ b/kernel/bpf/ringbuf.c @@ -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); -- 2.29.2
