Commit 927cbb47 authored by Hou Tao's avatar Hou Tao Committed by Andrii Nakryiko
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libbpf: Handle size overflow for ringbuf mmap 



The maximum size of ringbuf is 2GB on x86-64 host, so 2 * max_entries
will overflow u32 when mapping producer page and data pages. Only
casting max_entries to size_t is not enough, because for 32-bits
application on 64-bits kernel the size of read-only mmap region
also could overflow size_t.

So fixing it by casting the size of read-only mmap region into a __u64
and checking whether or not there will be overflow during mmap.

Fixes: bf99c936 ("libbpf: Add BPF ring buffer support")
Signed-off-by: default avatarHou Tao <houtao1@huawei.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221116072351.1168938-3-houtao@huaweicloud.com
parent 689eb2f1

tools/lib/bpf/ringbuf.c

+8 −4
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ int ring_buffer__add(struct ring_buffer *rb, int map_fd, 
	__u32 len = sizeof(info);

	struct epoll_event *e;

	struct ring *r;

	__u64 mmap_sz;

	void *tmp;

	int err;
@@ -115,8 +116,7 @@ int ring_buffer__add(struct ring_buffer *rb, int map_fd, 
	r->mask = info.max_entries - 1;



	/* Map writable consumer page */

	tmp = mmap(NULL, rb->page_size, PROT_READ | PROT_WRITE, MAP_SHARED,

		   map_fd, 0);

	tmp = mmap(NULL, rb->page_size, PROT_READ | PROT_WRITE, MAP_SHARED, map_fd, 0);

	if (tmp == MAP_FAILED) {

		err = -errno;

		pr_warn("ringbuf: failed to mmap consumer page for map fd=%d: %d\n",
@@ -129,8 +129,12 @@ int ring_buffer__add(struct ring_buffer *rb, int map_fd, 
	 * data size to allow simple reading of samples that wrap around the

	 * end of a ring buffer. See kernel implementation for details.

	 * */

	tmp = mmap(NULL, rb->page_size + 2 * info.max_entries, PROT_READ,

		   MAP_SHARED, map_fd, rb->page_size);

	mmap_sz = rb->page_size + 2 * (__u64)info.max_entries;

	if (mmap_sz != (__u64)(size_t)mmap_sz) {

		pr_warn("ringbuf: ring buffer size (%u) is too big\n", info.max_entries);

		return libbpf_err(-E2BIG);

	}

	tmp = mmap(NULL, (size_t)mmap_sz, PROT_READ, MAP_SHARED, map_fd, rb->page_size);

	if (tmp == MAP_FAILED) {

		err = -errno;

		ringbuf_unmap_ring(rb, r);