From: Ralph Campbell <rcampbell@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx> Signed-off-by: Jérôme Glisse <jglisse@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/hmm.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff -puN mm/hmm.c~mm-hmm-fix-uninitialized-use-of-entry-in-hmm_vma_walk_pmd mm/hmm.c --- a/mm/hmm.c~mm-hmm-fix-uninitialized-use-of-entry-in-hmm_vma_walk_pmd +++ a/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. _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
