CVE-2026-74378: RDMA/rxe: Fix TOCTOU heap overflow in get_srq_wqe

From: Greg Kroah-Hartman <[email protected]>

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2026-74378 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 4.8 with commit 8700e3e7c4857d28ebaa824509934556da0b3e76 and fixed in 6.1.178 with commit 3cfa2a3adc51b7c57729961a03446962ff10e3d2
	Issue introduced in 4.8 with commit 8700e3e7c4857d28ebaa824509934556da0b3e76 and fixed in 6.6.145 with commit cd19a6345e3727adafafa5954b58b13c92e13b80
	Issue introduced in 4.8 with commit 8700e3e7c4857d28ebaa824509934556da0b3e76 and fixed in 6.12.97 with commit 3e07ea9579dc9553d2285c26c2823931358aa3b8
	Issue introduced in 4.8 with commit 8700e3e7c4857d28ebaa824509934556da0b3e76 and fixed in 6.18.40 with commit 02558c86b6b761063e9399e6b939984500327ef1
	Issue introduced in 4.8 with commit 8700e3e7c4857d28ebaa824509934556da0b3e76 and fixed in 7.1.5 with commit b9800d7953d119bcc068c74587d48e4ba0313629
	Issue introduced in 4.8 with commit 8700e3e7c4857d28ebaa824509934556da0b3e76 and fixed in 7.2-rc1 with commit 22b8fbded65b8c441b634a185f8da67657df6c50

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-74378
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/infiniband/sw/rxe/rxe_resp.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/3cfa2a3adc51b7c57729961a03446962ff10e3d2
	https://git.kernel.org/stable/c/cd19a6345e3727adafafa5954b58b13c92e13b80
	https://git.kernel.org/stable/c/3e07ea9579dc9553d2285c26c2823931358aa3b8
	https://git.kernel.org/stable/c/02558c86b6b761063e9399e6b939984500327ef1
	https://git.kernel.org/stable/c/b9800d7953d119bcc068c74587d48e4ba0313629
	https://git.kernel.org/stable/c/22b8fbded65b8c441b634a185f8da67657df6c50