This is a note to let you know that I've just added the patch titled libbpf: Handle size overflow for ringbuf mmap to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: libbpf-handle-size-overflow-for-ringbuf-mmap.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 17e6987448385baa7747845d66da6c0669609cb3 Author: Hou Tao <houtao1@xxxxxxxxxx> Date: Wed Nov 16 15:23:49 2022 +0800 libbpf: Handle size overflow for ringbuf mmap [ 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@xxxxxxxxxx> Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx> Link: https://lore.kernel.org/bpf/20221116072351.1168938-3-houtao@xxxxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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 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);