From effc1b25088502fbd30305c79773de2d1f7470a6 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Fri, 10 Nov 2017 04:27:37 +1100 Subject: [PATCH] powerpc/64s/hash: Fix fork() with 512TB process address space Hash unconditionally resets the addr_limit to default (128TB) when the mm context is initialised. If a process has > 128TB mappings when it forks, the child will not get the 512TB addr_limit, so accesses to valid > 128TB mappings will fail in the child. Fix this by only resetting the addr_limit to default if it was 0. Non zero indicates it was duplicated from the parent (0 means exec()). Fixes: f4ea6dcb08ea ("powerpc/mm: Enable mappings above 128TB") Cc: stable@vger.kernel.org # v4.12+ Signed-off-by: Nicholas Piggin Reviewed-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman --- arch/powerpc/mm/mmu_context_book3s64.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c index 6d724da..846cbad 100644 --- a/arch/powerpc/mm/mmu_context_book3s64.c +++ b/arch/powerpc/mm/mmu_context_book3s64.c @@ -93,11 +93,11 @@ static int hash__init_new_context(struct mm_struct *mm) return index; /* - * We do switch_slb() early in fork, even before we setup the - * mm->context.addr_limit. Default to max task size so that we copy the - * default values to paca which will help us to handle slb miss early. + * In the case of exec, use the default limit, + * otherwise inherit it from the mm we are duplicating. */ - mm->context.addr_limit = DEFAULT_MAP_WINDOW_USER64; + if (!mm->context.addr_limit) + mm->context.addr_limit = DEFAULT_MAP_WINDOW_USER64; /* * The old code would re-promote on fork, we don't do that when using -- 2.7.4