The patch titled
Subject: mm/page_alloc.c: avoid potential NULL pointer dereference
has been added to the -mm tree. Its filename is
mm-page_alloc-avoid-potential-null-pointer-dereference.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-avoid-potential-null-pointer-dereference.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-avoid-potential-null-pointer-dereference.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Subject: mm/page_alloc.c: avoid potential NULL pointer dereference
ac.preferred_zoneref->zone passed to alloc_flags_nofragment() can be NULL.
'zone' pointer unconditionally derefernced in alloc_flags_nofragment().
Bail out on NULL zone to avoid potential crash. Currently we don't see
any crashes only because alloc_flags_nofragment() has another bug which
allows compiler to optimize away all accesses to 'zone'.
Link: http://lkml.kernel.org/r/20190423120806.3503-1-aryabinin@xxxxxxxxxxxxx
Fixes: 6bb154504f8b ("mm, page_alloc: spread allocations across zones before introducing fragmentation")
Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 3 +++
1 file changed, 3 insertions(+)
--- a/mm/page_alloc.c~mm-page_alloc-avoid-potential-null-pointer-dereference
+++ a/mm/page_alloc.c
@@ -3432,6 +3432,9 @@ alloc_flags_nofragment(struct zone *zone
alloc_flags |= ALLOC_KSWAPD;
#ifdef CONFIG_ZONE_DMA32
+ if (!zone)
+ return alloc_flags;
+
if (zone_idx(zone) != ZONE_NORMAL)
goto out;
_
Patches currently in -mm which might be from aryabinin@xxxxxxxxxxxxx are
mm-page_alloc-avoid-potential-null-pointer-dereference.patch
mm-page_alloc-fix-never-set-alloc_nofragment-flag.patch
mm-vmscan-remove-unused-lru_pages-argument.patch
