From: Hou Tao houtao1@huawei.com
[ Upstream commit 927cbb478adf917e0a142b94baa37f06279cc466 ]
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: bf99c936f947 ("libbpf: Add BPF ring buffer support") Signed-off-by: Hou Tao houtao1@huawei.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20221116072351.1168938-3-houtao@huaweicloud.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/ringbuf.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c index 86c31c787fb9..141dbaf6e828 100644 --- a/tools/lib/bpf/ringbuf.c +++ b/tools/lib/bpf/ringbuf.c @@ -59,6 +59,7 @@ 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;
@@ -97,8 +98,7 @@ 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", @@ -111,8 +111,12 @@ 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 -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);