The patch titled Subject: mm/cma: fix alloc_contig_range ret code/potential leak has been removed from the -mm tree. Its filename was mm-cma-fix-alloc_contig_range-ret-code-potential-leak.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------ From: Mike Kravetz mike.kravetz@oracle.com Subject: mm/cma: fix alloc_contig_range ret code/potential leak
In an attempt to make contiguous allocation routines more available to drivers, I have been experimenting with code similar to that used by alloc_gigantic_page(). While stressing this code with many other allocations and frees in progress, I would sometimes notice large 'leaks' of page ranges.
I traced this down to the routine alloc_contig_range() itself. In 8ef5849fa8a2 ("mm/cma: always check which page caused allocation failure") the code was changed so that an -EBUSY returned by __alloc_contig_migrate_range() would not immediately return to the caller. Rather, processing continues so that test_pages_isolated() is eventually called. This is done because test_pages_isolated() has a tracepoint to identify the busy pages.
However, it is possible (observed in my testing) that pages which were busy when __alloc_contig_migrate_range was called may become available by the time test_pages_isolated is called. Further, it is possible that the entire range can actually be allocated. Unfortunately, in this case the return code originally set by __alloc_contig_migrate_range (-EBUSY) is returned to the calller. Therefore, the caller assumes the range was not allocated and the pages are essentially leaked.
The following patch simply updates the return code based on the value returned from test_pages_isolated.
It is unlikely that we will hit this issue today based on the limited number of callers to alloc_contig_range. However, I have Cc'ed stable because if we do hit this issue it has the potential to leak a large number of pages.
If the call __alloc_contig_migrate_range() in alloc_contig_range returns -EBUSY, processing continues so that test_pages_isolated() is called where there is a tracepoint to identify the busy pages. However, it is possible for busy pages to become available between the calls to these two routines. In this case, the range of pages may be allocated. Unfortunately, the original return code (ret == -EBUSY) is still set and returned to the caller. Therefore, the caller believes the pages were not allocated and they are leaked.
Update the return code with the value from test_pages_isolated().
Link: http://lkml.kernel.org/r/20171120193930.23428-2-mike.kravetz@oracle.com Fixes: 8ef5849fa8a2 ("mm/cma: always check which page caused allocation failure") Signed-off-by: Mike Kravetz mike.kravetz@oracle.com Acked-by: Michal Hocko mhocko@suse.com Acked-by: Michal Nazarewicz mina86@mina86.com Acked-by: Vlastimil Babka vbabka@suse.cz Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Laura Abbott labbott@redhat.com Cc: Michal Hocko mhocko@suse.com Cc: Mel Gorman mgorman@techsingularity.net Cc: Johannes Weiner hannes@cmpxchg.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/page_alloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff -puN mm/page_alloc.c~mm-cma-fix-alloc_contig_range-ret-code-potential-leak mm/page_alloc.c --- a/mm/page_alloc.c~mm-cma-fix-alloc_contig_range-ret-code-potential-leak +++ a/mm/page_alloc.c @@ -7702,10 +7702,10 @@ int alloc_contig_range(unsigned long sta }
/* Make sure the range is really isolated. */ - if (test_pages_isolated(outer_start, end, false)) { + ret = test_pages_isolated(outer_start, end, false); + if (ret) { pr_info_ratelimited("%s: [%lx, %lx) PFNs busy\n", __func__, outer_start, end); - ret = -EBUSY; goto done; }
_
Patches currently in -mm which might be from mike.kravetz@oracle.com are
mm-cma-fix-alloc_contig_range-ret-code-potential-leak-v2.patch