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Jinjiang Tu 6addb2d950 mm: fix NULL pointer dereference in alloc_pages_bulk_noprof 
commit 8ce41b0f9d upstream.

We triggered a NULL pointer dereference for ac.preferred_zoneref->zone in
alloc_pages_bulk_noprof() when the task is migrated between cpusets.

When cpuset is enabled, in prepare_alloc_pages(), ac->nodemask may be
&current->mems_allowed.  when first_zones_zonelist() is called to find
preferred_zoneref, the ac->nodemask may be modified concurrently if the
task is migrated between different cpusets.  Assuming we have 2 NUMA Node,
when traversing Node1 in ac->zonelist, the nodemask is 2, and when
traversing Node2 in ac->zonelist, the nodemask is 1.  As a result, the
ac->preferred_zoneref points to NULL zone.

In alloc_pages_bulk_noprof(), for_each_zone_zonelist_nodemask() finds a
allowable zone and calls zonelist_node_idx(ac.preferred_zoneref), leading
to NULL pointer dereference.

__alloc_pages_noprof() fixes this issue by checking NULL pointer in commit
ea57485af8 ("mm, page_alloc: fix check for NULL preferred_zone") and
commit df76cee6bb ("mm, page_alloc: remove redundant checks from alloc
fastpath").

To fix it, check NULL pointer for preferred_zoneref->zone.

Link: https://lkml.kernel.org/r/20241113083235.166798-1-tujinjiang@huawei.com
Fixes: 387ba26fb1 ("mm/page_alloc: add a bulk page allocator")
Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Lobakin <alobakin@pm.me>
Cc: David Hildenbrand <david@redhat.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2024-11-22 15:37:30 +01:00
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README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.