From 8d63e4cd62b2583c7efe64f2ede406b3f44983f6 Mon Sep 17 00:00:00 2001 From: Ralph Campbell Date: Wed, 31 Jan 2018 16:20:30 -0800 Subject: mm/hmm: fix uninitialized use of 'entry' in hmm_vma_walk_pmd() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Jérôme Glisse Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/hmm.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'mm') 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. -- cgit v1.2.3-59-g8ed1b