mm/hmm: fix uninitialized use of 'entry' in hmm_vma_walk_pmd()
authorRalph Campbell <rcampbell@nvidia.com>
Thu, 1 Feb 2018 00:20:30 +0000 (16:20 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 1 Feb 2018 01:18:40 +0000 (17:18 -0800)
commit8d63e4cd62b2583c7efe64f2ede406b3f44983f6
tree9db2787ac3a37bd5ab9f08c5020158a8fc02d1b6
parentdef9b71ee651a6fee93a10734b94f93a69cdb2d4
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>
mm/hmm.c