linux-cve-announce - CVE-2024-57839: Revert "readahead: properly shorten readahead when falling back to do_page_cache

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Message-ID: <2025011101-CVE-2024-57839-daf6@gregkh>
Date: Sat, 11 Jan 2025 15:31:02 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-57839: Revert "readahead: properly shorten readahead when falling back to do_page_cache_ra()"

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

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

Revert "readahead: properly shorten readahead when falling back to do_page_cache_ra()"

This reverts commit 7c877586da3178974a8a94577b6045a48377ff25.

Anders and Philippe have reported that recent kernels occasionally hang
when used with NFS in readahead code.  The problem has been bisected to
7c877586da3 ("readahead: properly shorten readahead when falling back to
do_page_cache_ra()").  The cause of the problem is that ra->size can be
shrunk by read_pages() call and subsequently we end up calling
do_page_cache_ra() with negative (read huge positive) number of pages. 
Let's revert 7c877586da3 for now until we can find a proper way how the
logic in read_pages() and page_cache_ra_order() can coexist.  This can
lead to reduced readahead throughput due to readahead window confusion but
that's better than outright hangs.

The Linux kernel CVE team has assigned CVE-2024-57839 to this issue.

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

	Issue introduced in 6.11 with commit 7c877586da3178974a8a94577b6045a48377ff25 and fixed in 6.12.5 with commit 85351e4941a253e4c50fb7048bfc19b60b4ec44b
	Issue introduced in 6.11 with commit 7c877586da3178974a8a94577b6045a48377ff25 and fixed in 6.13-rc2 with commit a220d6b95b1ae12c7626283d7609f0a1438e6437

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-2024-57839
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:
	mm/readahead.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/85351e4941a253e4c50fb7048bfc19b60b4ec44b
	https://git.kernel.org/stable/c/a220d6b95b1ae12c7626283d7609f0a1438e6437