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authorRalph Campbell <rcampbell@nvidia.com>2018-01-31 16:20:30 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-01-31 17:18:40 -0800
commit8d63e4cd62b2583c7efe64f2ede406b3f44983f6 (patch)
tree9db2787ac3a37bd5ab9f08c5020158a8fc02d1b6
parentdef9b71ee651a6fee93a10734b94f93a69cdb2d4 (diff)
mm/hmm: fix uninitialized use of 'entry' in hmm_vma_walk_pmd()
The variable 'entry' is used before being initialized in hmm_vma_walk_pmd(). No bad effect (beside performance hit) so !non_swap_entry(0) evaluate to true which trigger a fault as if CPU was trying to access migrated memory and migrate memory back from device memory to regular memory. This function (hmm_vma_walk_pmd()) is called when a device driver tries to populate its own page table. For migrated memory it should not happen as the device driver should already have populated its page table correctly during the migration. Only case I can think of is multi-GPU where a second GPU triggers migration back to regular memory. Again this would just result in a performance hit, nothing bad would happen. Link: http://lkml.kernel.org/r/20180122185759.26286-1-jglisse@redhat.com Signed-off-by: Ralph Campbell <rcampbell@nvidia.com> Signed-off-by: Jérôme Glisse <jglisse@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/hmm.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/mm/hmm.c b/mm/hmm.c
index ea19742a5d60..979211c7ccc8 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -418,7 +418,7 @@ again:
}
if (!pte_present(pte)) {
- swp_entry_t entry;
+ swp_entry_t entry = pte_to_swp_entry(pte);
if (!non_swap_entry(entry)) {
if (hmm_vma_walk->fault)
@@ -426,8 +426,6 @@ again:
continue;
}
- entry = pte_to_swp_entry(pte);
-
/*
* This is a special swap entry, ignore migration, use
* device and report anything else as error.