4.14-stable review patch. If anyone has any objections, please let me know.
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From: Nicholas Piggin npiggin@gmail.com
commit effc1b25088502fbd30305c79773de2d1f7470a6 upstream.
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") Signed-off-by: Nicholas Piggin npiggin@gmail.com Reviewed-by: Aneesh Kumar K.V aneesh.kumar@linux.vnet.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/mm/mmu_context_book3s64.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
--- 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 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