Patch "powerpc/64s/hash: Fix fork() with 512TB process address space" has been added to the 4.14-stable tree

Patch "powerpc/64s/hash: Fix fork() with 512TB process address space" has been added to the 4.14-stable tree

[gregkh]

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;a=summary

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