CVE-2026-46320: tap: free page on error paths in tap_get_user_xdp()

CVE-2026-46320: tap: free page on error paths in tap_get_user_xdp()

[Greg Kroah-Hartman]

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

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

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

tap: free page on error paths in tap_get_user_xdp()

tap_get_user_xdp() rejects a frame shorter than ETH_HLEN with -EINVAL,
and returns -ENOMEM when build_skb() fails. Both paths jump to the err
label without freeing the page that vhost_net_build_xdp() allocated for
the frame. tap_sendmsg() discards the per-buffer return value and always
returns 0, so vhost_tx_batch() takes the success path and never frees
the page; each rejected frame in a batch leaks one page-frag chunk.

Free the page on both error paths, before the skb is built. This is the
tap counterpart of the same leak in tun_xdp_one().

The Linux kernel CVE team has assigned CVE-2026-46320 to this issue.


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

	Issue introduced in 4.20 with commit 0efac27791ee068075d80f07c55a229b1335ce12 and fixed in 7.0.12 with commit 18a84c35842e19cd3c5534d8cee73d31863f696d
	Issue introduced in 4.20 with commit 0efac27791ee068075d80f07c55a229b1335ce12 and fixed in 7.1-rc6 with commit 3bcf7aec6a9d16438f2cec29f5d7c8d5b8edf9b2

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-2026-46320
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/tap.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/18a84c35842e19cd3c5534d8cee73d31863f696d
	https://git.kernel.org/stable/c/3bcf7aec6a9d16438f2cec29f5d7c8d5b8edf9b2