Subject: CVE-2024-41066: ibmvnic: Add tx check to prevent skb leak

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

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

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

ibmvnic: Add tx check to prevent skb leak

Below is a summary of how the driver stores a reference to an skb during
transmit:
    tx_buff[free_map[consumer_index]]->skb = new_skb;
    free_map[consumer_index] = IBMVNIC_INVALID_MAP;
    consumer_index ++;
Where variable data looks like this:
    free_map == [4, IBMVNIC_INVALID_MAP, IBMVNIC_INVALID_MAP, 0, 3]
                                               	consumer_index^
    tx_buff == [skb=null, skb=<ptr>, skb=<ptr>, skb=null, skb=null]

The driver has checks to ensure that free_map[consumer_index] pointed to
a valid index but there was no check to ensure that this index pointed
to an unused/null skb address. So, if, by some chance, our free_map and
tx_buff lists become out of sync then we were previously risking an
skb memory leak. This could then cause tcp congestion control to stop
sending packets, eventually leading to ETIMEDOUT.

Therefore, add a conditional to ensure that the skb address is null. If
not then warn the user (because this is still a bug that should be
patched) and free the old pointer to prevent memleak/tcp problems.

The Linux kernel CVE team has assigned CVE-2024-41066 to this issue.

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

	Fixed in 6.1.101 with commit 16ad1557cae5
	Fixed in 6.6.42 with commit 267c61c4afed
	Fixed in 6.9.11 with commit e7b75def33ea
	Fixed in 6.10 with commit 0983d288caf9

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-2024-41066
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/ibm/ibmvnic.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/16ad1557cae582e79bb82dddd612d9bdfaa11d4c
	https://git.kernel.org/stable/c/267c61c4afed0ff9a2e83462abad3f41d8ca1f06
	https://git.kernel.org/stable/c/e7b75def33eae61ddaad6cb616c517dc3882eb2a
	https://git.kernel.org/stable/c/0983d288caf984de0202c66641577b739caad561