oss-security - CVE-2022-22942: Linux kernel: wrong file descriptor handling in the vmwgfx driver

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Date: Thu, 27 Jan 2022 21:00:19 +0100
From: Mathias Krause <minipli@...ecurity.net>
To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com>
Cc: Zack Rusin <zackr@...are.com>
Subject: CVE-2022-22942: Linux kernel: wrong file descriptor handling in the
 vmwgfx driver

Hi!

A vulnerability was found in the vmwgfx driver that allows unprivileged
users to gain access to files opened by other processes on the system
through a dangling 'file' pointer.

Exploiting this vulnerability requires an attacker to have access to
either /dev/dri/card0 or /dev/dri/rendererD128 and be able to issue an
ioctl() on the resulting file descriptor.

Linux kernels making use of the vmwgfx driver and containing commit
c906965dee22 ("drm/vmwgfx: Add export fence to file descriptor support")
are affected, which is v4.14+.

If the vmwgfx driver isn't loaded, your system isn't affected.

Systems using the VMWare graphics card emulated by QEMU (-vga vmware)
aren't affected either, as these lack a required feature that makes the
driver fail to load.

Attached are patches as have been sent to linux-distros on Jan. 21st.
They're against mainline Linux (0001-*.patch) or backports for all
affected kernels (backport-*.patch) respectively. They should soon be
merged into the corresponding Linux kernel trees.

CVE-2022-22942 was allocated for this issue.

Thanks,
Mathias
View attachment "backport-5.16-drm-vmwgfx-Fix-stale-file-descriptors-on-failed-user.patch" of type "text/x-patch" (5567 bytes)

View attachment "backport-4.19-drm-vmwgfx-Fix-stale-file-descriptors-on-failed-user.patch" of type "text/x-patch" (5616 bytes)

View attachment "0001-drm-vmwgfx-Fix-stale-file-descriptors-on-failed-user.patch" of type "text/x-patch" (5509 bytes)

Download attachment "OpenPGP_signature" of type "application/pgp-signature" (666 bytes)

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