In the Linux kernel, the following vulnerability has been resolved:
io_uring/net: fix slab-out-of-bounds read in io_bundle_nbufs()
sqe->len is __u32 but gets stored into sr->len which is int. When userspace passes sqe->len values exceeding INT_MAX (e.g. 0xFFFFFFFF), sr->len overflows to a negative value. This negative value propagates through the bundle recv/send path:
- io_recv(): sel.val = sr->len (ssize_t gets -1)
- io_recv_buf_select(): arg.max_len = sel->val (size_t gets
- io_ring_buffers_peek(): buf->len is not clamped because max_len
- iov[].iov_len = 0xFFFFFFFF flows into io_bundle_nbufs()
- io_bundle_nbufs(): min_t(int, 0xFFFFFFFF, ret) yields -1,
This results in a slab-out-of-bounds read in io_bundle_nbufs() from the kmalloc-64 slab, as nbufs increments past the allocated iovec entries.
BUG: KASAN: slab-out-of-bounds in io_bundle_nbufs+0x128/0x160 Read of size 8 at addr ffff888100ae05c8 by task exp/145 Call Trace: io_bundle_nbufs+0x128/0x160 io_recv_finish+0x117/0xe20 io_recv+0x2db/0x1160
Fix this by rejecting negative sr->len values early in both io_sendmsg_prep() and io_recvmsg_prep(). Since sqe->len is __u32, any value > INT_MAX indicates overflow and is not a valid length.