Subject: CVE-2024-35882: SUNRPC: Fix a slow server-side memory leak with RPC-over-TCP

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

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

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

SUNRPC: Fix a slow server-side memory leak with RPC-over-TCP

Jan Schunk reports that his small NFS servers suffer from memory
exhaustion after just a few days. A bisect shows that commit
e18e157bb5c8 ("SUNRPC: Send RPC message on TCP with a single
sock_sendmsg() call") is the first bad commit.

That commit assumed that sock_sendmsg() releases all the pages in
the underlying bio_vec array, but the reality is that it doesn't.
svc_xprt_release() releases the rqst's response pages, but the
record marker page fragment isn't one of those, so it is never
released.

This is a narrow fix that can be applied to stable kernels. A
more extensive fix is in the works.

The Linux kernel CVE team has assigned CVE-2024-35882 to this issue.

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

	Issue introduced in 6.6 with commit e18e157bb5c8 and fixed in 6.6.26 with commit 1ba1291172f9
	Issue introduced in 6.6 with commit e18e157bb5c8 and fixed in 6.8.5 with commit a2ebedf7bcd1
	Issue introduced in 6.6 with commit e18e157bb5c8 and fixed in 6.9 with commit 05258a0a69b3

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-2024-35882
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/sunrpc/svcsock.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/1ba1291172f935e6b6fe703161a948f3347400b8
	https://git.kernel.org/stable/c/a2ebedf7bcd17a1194a0a18122c885eb578ee882
	https://git.kernel.org/stable/c/05258a0a69b3c5d2c003f818702c0a52b6fea861