mm/migrate: fix indexing bug (off by one) and avoid out of bound access

Index was incremented before last use and thus the second array could
dereference to an invalid address (not mentioning the fact that it did
not properly clear the entry we intended to clear).

Link: http://lkml.kernel.org/r/1506973525-16491-1-git-send-email-jglisse@redhat.com
Fixes: 8315ada7f095bf ("mm/migrate: allow migrate_vma() to alloc new page on empty entry")
Signed-off-by: Mark Hairgrove <mhairgrove@nvidia.com>
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/migrate.c b/mm/migrate.c
index 6954c1435833133f910a08a9cd8e0e1516084296..e00814ca390ea46dab6174e3c7c183e7bd4faf73 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2146,8 +2146,9 @@ static int migrate_vma_collect_hole(unsigned long start,
        unsigned long addr;
 
        for (addr = start & PAGE_MASK; addr < end; addr += PAGE_SIZE) {
-               migrate->src[migrate->npages++] = MIGRATE_PFN_MIGRATE;
+               migrate->src[migrate->npages] = MIGRATE_PFN_MIGRATE;
                migrate->dst[migrate->npages] = 0;
+               migrate->npages++;
                migrate->cpages++;
        }