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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: bf99c936f9 ("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
This commit is contained in:
Hou Tao 2022-11-16 15:23:49 +08:00 committed by Andrii Nakryiko
parent 689eb2f1ba
commit 927cbb478a
1 changed files with 8 additions and 4 deletions
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12
tools/lib/bpf/ringbuf.c
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@ -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);