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From fe50aa4374f20333d9b077bbe09397d38112b081 Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Tue, 28 Nov 2017 11:26:57 +0100
Subject: [PATCH 4/5] powerpc/64s/hash: Fix fork() with 512TB process address
space
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(-)
diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c
index a75f63833284..bb9cdf01fc4f 100644
--- a/arch/powerpc/mm/mmu_context_book3s64.c
+++ b/arch/powerpc/mm/mmu_context_book3s64.c
@@ -95,11 +95,11 @@ 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
--
2.14.3
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