CVE-2026-64124: net: devmem: reject dma-buf bind with non-page-aligned size or SG length

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

net: devmem: reject dma-buf bind with non-page-aligned size or SG length

net_devmem_bind_dmabuf() trusts dmabuf->size and sg_dma_len() to be
PAGE_SIZE multiples without checking:

  - tx_vec is sized dmabuf->size / PAGE_SIZE, and
    net_devmem_get_niov_at() only bounds-checks virt_addr < dmabuf->size
    before indexing tx_vec[virt_addr / PAGE_SIZE]. With size =
    N*PAGE_SIZE + r (1 <= r < PAGE_SIZE), sendmsg() at iov_base =
    N*PAGE_SIZE passes the bound check and reads tx_vec[N] -- one past.

  - owner->area.num_niovs = len / PAGE_SIZE while gen_pool_add_owner()
    covers the full byte len, so a non-page-multiple non-final sg
    desyncs num_niovs from the gen_pool region for every later sg, on
    both RX and TX.

dma-buf does not require page-aligned sizes, so the bind path has to
enforce what its own indexing assumes. Reject both with -EINVAL.

The size check is TX-only (only tx_vec is sized off dmabuf->size); the
SG-length check covers both directions.

The Linux kernel CVE team has assigned CVE-2026-64124 to this issue.


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

	Issue introduced in 6.16 with commit bd61848900bff597764238f3a8ec67c815cd316e and fixed in 6.18.35 with commit 134c517dfa63203287b2aad6558017f42435a02e
	Issue introduced in 6.16 with commit bd61848900bff597764238f3a8ec67c815cd316e and fixed in 7.0.11 with commit d5008e4e4ee6b739256b796702a7d1aae1b5c3b4
	Issue introduced in 6.16 with commit bd61848900bff597764238f3a8ec67c815cd316e and fixed in 7.1 with commit 4eb82ba543421e9e38cc14e4e82058b78850df50

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-2026-64124
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/core/devmem.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/134c517dfa63203287b2aad6558017f42435a02e
	https://git.kernel.org/stable/c/d5008e4e4ee6b739256b796702a7d1aae1b5c3b4
	https://git.kernel.org/stable/c/4eb82ba543421e9e38cc14e4e82058b78850df50