This is a note to let you know that I've just added the patch titled

powerpc/64s/hash: Fix fork() with 512TB process address space

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: powerpc-64s-hash-fix-fork-with-512tb-process-address-space.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From effc1b25088502fbd30305c79773de2d1f7470a6 Mon Sep 17 00:00:00 2001

From: Nicholas Piggin npiggin@gmail.com Date: Fri, 10 Nov 2017 04:27:37 +1100 Subject: powerpc/64s/hash: Fix fork() with 512TB process address space

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

Patches currently in stable-queue which might be from npiggin@gmail.com are

queue-4.14/powerpc-64s-hash-fix-128tb-512tb-virtual-address-boundary-case-allocation.patch queue-4.14/powerpc-64s-hash-fix-fork-with-512tb-process-address-space.patch queue-4.14/powerpc-64s-radix-fix-128tb-512tb-virtual-address-boundary-case-allocation.patch queue-4.14/powerpc-64s-hash-allow-map_fixed-allocations-to-cross-128tb-boundary.patch queue-4.14/powerpc-64s-hash-fix-512t-hint-detection-to-use-128t.patch