CVE-2026-74435: rxrpc: rxrpc_verify_data ensure rx_dec_buffer alloc

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

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

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

rxrpc: rxrpc_verify_data ensure rx_dec_buffer alloc

rxrpc_recvmsg_data() calls rxrpc_verify_data() whenever the
rxrpc_call.rx_dec_buffer is unallocated and assumes that upon
successful return that rx_dec_buffer must be allocated.
However, rxrpc_verify_data() does not request an allocation if
the rxrpc_skb_priv.len is zero.

In addition, failure to allocate rx_dec_buffer will result in a
call to skb_copy_bits() with a NULL destination which can
trigger a NULL pointer dereference.

To prevent these issues rxrpc_verify_data() is modified to
always attempt to allocate the rxrpc_call.rx_dec_buffer if it
is NULL.

This issue was identified with assistance of a private
sashiko instance.

The Linux kernel CVE team has assigned CVE-2026-74435 to this issue.


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

	Issue introduced in 6.6.143 with commit a05bf6d9e621fa71e89ccebe3047ba45218d7b38 and fixed in 6.6.145 with commit 8bbede0afced346b24e4fbde0c68cf12980ba948
	Issue introduced in 6.12.93 with commit b94a6ccbaf1104dd980150a65fdeb2f69d17d2f5 and fixed in 6.12.97 with commit 6563b4eb38c35d75892445bcf8aacdc29914821c
	Issue introduced in 6.18.35 with commit 46cb765e2e5ad52303ea157e10d370bb6b7acbbf and fixed in 6.18.40 with commit d3b642cf95d48234590cc91450d8705a9bf6b540
	Issue introduced in 7.1 with commit d2bc90cf6c75cb96d2ce549be6c35efa3099d25b and fixed in 7.1.5 with commit a962bc8508592c4d51092edac68579bd8b18fe44
	Issue introduced in 7.1 with commit d2bc90cf6c75cb96d2ce549be6c35efa3099d25b and fixed in 7.2-rc1 with commit 16c8ae9735c5bd7e54dd7478d6348e0fc860842d
	Issue introduced in 7.0.11 with commit c580087743712112778a06d65a4074053072d7bf

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-2026-74435
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:
	net/rxrpc/recvmsg.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/8bbede0afced346b24e4fbde0c68cf12980ba948
	https://git.kernel.org/stable/c/6563b4eb38c35d75892445bcf8aacdc29914821c
	https://git.kernel.org/stable/c/d3b642cf95d48234590cc91450d8705a9bf6b540
	https://git.kernel.org/stable/c/a962bc8508592c4d51092edac68579bd8b18fe44
	https://git.kernel.org/stable/c/16c8ae9735c5bd7e54dd7478d6348e0fc860842d