CVE-2026-74545: rtase: fix double free of multi-frag skb on DMA map failure

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

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

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

rtase: fix double free of multi-frag skb on DMA map failure

In rtase_start_xmit(), when the head buffer DMA mapping fails after
rtase_xmit_frags() has mapped all fragments, the error path clears
the fragment descriptors with rtase_tx_clear_range(), which frees
the skb through the last-frag slot and accounts tx_dropped. Control
then falls through to the common error label, which frees the same
skb a second time and counts it again.

Return right after clearing the fragments when the skb owns frags;
the no-frag case still drops through and frees the head skb once.

The Linux kernel CVE team has assigned CVE-2026-74545 to this issue.


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

	Issue introduced in 6.12 with commit d6e882b89fdf80be0ab4f914ec10f75215e49495 and fixed in 6.12.103 with commit 4f09172aff5f73a5e914f4fbc0d00a1c2ea9f7cb
	Issue introduced in 6.12 with commit d6e882b89fdf80be0ab4f914ec10f75215e49495 and fixed in 6.18.44 with commit db986098f30881fafcc752800aa3b13fd289c922
	Issue introduced in 6.12 with commit d6e882b89fdf80be0ab4f914ec10f75215e49495 and fixed in 7.1.8 with commit de691dc3227b061c4d0beba9f0128fe1ff33dd68
	Issue introduced in 6.12 with commit d6e882b89fdf80be0ab4f914ec10f75215e49495 and fixed in 7.2-rc6 with commit 6fb7b769d6ed6d1d2e02af4a80e57a2477f35086

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-2026-74545
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/realtek/rtase/rtase_main.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/4f09172aff5f73a5e914f4fbc0d00a1c2ea9f7cb
	https://git.kernel.org/stable/c/db986098f30881fafcc752800aa3b13fd289c922
	https://git.kernel.org/stable/c/de691dc3227b061c4d0beba9f0128fe1ff33dd68
	https://git.kernel.org/stable/c/6fb7b769d6ed6d1d2e02af4a80e57a2477f35086