In the Linux kernel, the following vulnerability has been resolved:
RDMA/rxe: Fix TOCTOU heap overflow in get_srq_wqe
get_srq_wqe() reads wqe->dma.num_sge from the shared receive queue buffer, which is mapped into userspace. It validates num_sge against max_sge, but then re-reads the same field to calculate the memcpy size. A concurrent userspace thread can modify num_sge between validation and use, causing a heap buffer overflow when copying the WQE into qp->resp.srq_wqe.
Read num_sge into a local variable and use it for both the bounds check and the size calculation.
References
- https://git.kernel.org/stable/c/02558c86b6b761063e9399e6b939984500327ef1
- https://git.kernel.org/stable/c/22b8fbded65b8c441b634a185f8da67657df6c50
- https://git.kernel.org/stable/c/3cfa2a3adc51b7c57729961a03446962ff10e3d2
- https://git.kernel.org/stable/c/3e07ea9579dc9553d2285c26c2823931358aa3b8
- https://git.kernel.org/stable/c/b9800d7953d119bcc068c74587d48e4ba0313629
- https://git.kernel.org/stable/c/cd19a6345e3727adafafa5954b58b13c92e13b80