CVE-2026-46181: RDMA/mlx4: Fix mis-use of RCU in mlx4_srq_event()

CVE-2026-46181: RDMA/mlx4: Fix mis-use of RCU in mlx4_srq_event()

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

In the Linux kernel, the following vulnerability has been resolved:

RDMA/mlx4: Fix mis-use of RCU in mlx4_srq_event()

Sashiko points out the radix_tree itself is RCU safe, but nothing ever
frees the mlx4_srq struct with RCU, and it isn't even accessed within the
RCU critical section. It also will crash if an event is delivered before
the srq object is finished initializing.

Use the spinlock since it isn't easy to make RCU work, use
refcount_inc_not_zero() to protect against partially initialized objects,
and order the refcount_set() to be after the srq is fully initialized.

The Linux kernel CVE team has assigned CVE-2026-46181 to this issue.


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

	Issue introduced in 4.9 with commit 30353bfc43a1602c020f31d95cf27182ffd23824 and fixed in 6.18.30 with commit 1e2a44875b6afb4add1115f7f3351dcbeb6f273d
	Issue introduced in 4.9 with commit 30353bfc43a1602c020f31d95cf27182ffd23824 and fixed in 7.0.7 with commit 8b7833f3bce35cb0d01c1503781523c099c675f0
	Issue introduced in 4.9 with commit 30353bfc43a1602c020f31d95cf27182ffd23824 and fixed in 7.1-rc3 with commit c9341307ea16b9395c2e4c9c94d8499d91fe31d0

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-2026-46181
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/net/ethernet/mellanox/mlx4/srq.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/1e2a44875b6afb4add1115f7f3351dcbeb6f273d
	https://git.kernel.org/stable/c/8b7833f3bce35cb0d01c1503781523c099c675f0
	https://git.kernel.org/stable/c/c9341307ea16b9395c2e4c9c94d8499d91fe31d0