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libbpf: Handle size overflow for user ringbuf mmap 

Similar with the overflow problem on ringbuf mmap, in user_ringbuf_map()
2 * max_entries may overflow u32 when mapping writeable region.

Fixing it by casting the size of writable mmap region into a __u64 and
checking whether or not there will be overflow during mmap.

Fixes: b66ccae01f ("bpf: Add libbpf logic for user-space ring buffer")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221116072351.1168938-4-houtao@huaweicloud.com
This commit is contained in:
Hou Tao 2022-11-16 15:23:50 +08:00 committed by Andrii Nakryiko
parent 927cbb478a
commit 64176bff24
1 changed files with 8 additions and 2 deletions
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10
tools/lib/bpf/ringbuf.c
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@ -352,6 +352,7 @@ static int user_ringbuf_map(struct user_ring_buffer *rb, int map_fd)
{
struct bpf_map_info info;
__u32 len = sizeof(info);
__u64 mmap_sz;
void *tmp;
struct epoll_event *rb_epoll;
int err;
@ -388,8 +389,13 @@ static int user_ringbuf_map(struct user_ring_buffer *rb, int map_fd)
* simple reading and writing of samples that wrap around the end of
* the buffer. See the kernel implementation for details.
*/
tmp = mmap(NULL, rb->page_size + 2 * info.max_entries,
PROT_READ | PROT_WRITE, 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("user ringbuf: ring buf size (%u) is too big\n", info.max_entries);
return -E2BIG;
}
tmp = mmap(NULL, (size_t)mmap_sz, PROT_READ | PROT_WRITE, MAP_SHARED,
map_fd, rb->page_size);
if (tmp == MAP_FAILED) {
err = -errno;
pr_warn("user ringbuf: failed to mmap data pages for map fd=%d: %d\n",