From: Ralph Campbell Date: Thu, 1 Feb 2018 00:20:30 +0000 (-0800) Subject: mm/hmm: fix uninitialized use of 'entry' in hmm_vma_walk_pmd() X-Git-Tag: v4.19~1701^2~15 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=8d63e4cd62b2583c7efe64f2ede406b3f44983f6;p=platform%2Fkernel%2Flinux-rpi.git 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 Signed-off-by: Jérôme Glisse Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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.