CVE-2026-74495: igbvf: Fix leak in TX DMA error cleanup

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

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

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

igbvf: Fix leak in TX DMA error cleanup

If an error is encountered while mapping TX buffers, the driver should
unmap any buffers already mapped for that skb.

Because count is incremented before each frag mapping, it will always
match the correct number of unmappings needed when dma_error is reached.
Decrementing count before the while loop in dma_error causes an
off-by-one error. If any mapping was successful before an unsuccessful
mapping, exactly one DMA mapping (the head) would leak.

This bug was introduced by a 2010 fix for an endless loop in dma_error.
All other affected drivers have already been fixed.

The Linux kernel CVE team has assigned CVE-2026-74495 to this issue.


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

	Issue introduced in 2.6.33 with commit c1fa347f20f17f14a4a1575727fa24340e8a9117 and fixed in 6.6.151 with commit 31089f4eab42e0fc248ec80c26f9b0bad59ba4cc
	Issue introduced in 2.6.33 with commit c1fa347f20f17f14a4a1575727fa24340e8a9117 and fixed in 6.12.103 with commit bc25d56c03e41c10bc4b40e99ca5d7b941675c04
	Issue introduced in 2.6.33 with commit c1fa347f20f17f14a4a1575727fa24340e8a9117 and fixed in 6.18.44 with commit 845a9cdd9b03b7b6fa8de3ee80579780350a7f65
	Issue introduced in 2.6.33 with commit c1fa347f20f17f14a4a1575727fa24340e8a9117 and fixed in 7.1.8 with commit df07003b5a6c6c9fce60d765d6a3da815a74c41c
	Issue introduced in 2.6.33 with commit c1fa347f20f17f14a4a1575727fa24340e8a9117 and fixed in 7.2-rc6 with commit 0565052b7e2f436b7f1541f4849da96dc0aa7a0e

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-2026-74495
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/intel/igbvf/netdev.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/31089f4eab42e0fc248ec80c26f9b0bad59ba4cc
	https://git.kernel.org/stable/c/bc25d56c03e41c10bc4b40e99ca5d7b941675c04
	https://git.kernel.org/stable/c/845a9cdd9b03b7b6fa8de3ee80579780350a7f65
	https://git.kernel.org/stable/c/df07003b5a6c6c9fce60d765d6a3da815a74c41c
	https://git.kernel.org/stable/c/0565052b7e2f436b7f1541f4849da96dc0aa7a0e