From 007ccec53da35528bd06fa0063da55b1311054c1 Mon Sep 17 00:00:00 2001
From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Date: Thu, 4 Feb 2016 12:24:46 +0100
Subject: [PATCH] s390/pageattr: do a single TLB flush for change_page_attr
The change of the access rights for an address range in the kernel
address space is currently done with a loop of IPTE + a store of the
modified PTE. Between the IPTE and the store the PTE will be invalid,
this intermediate state can cause problems with concurrent accesses.
Consider a change of a kernel area from read-write to read-only, a
concurrent reader of that area should be fine but with the invalid
PTE it might get an unexpected exception.
Remove the IPTEs for each PTE and do a global flush after all PTEs
have been modified.
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
arch/s390/mm/pageattr.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/arch/s390/mm/pageattr.c b/arch/s390/mm/pageattr.c
index 749c98407b41f..f2a5c29a97e9f 100644
--- a/arch/s390/mm/pageattr.c
+++ b/arch/s390/mm/pageattr.c
@@ -65,19 +65,17 @@ static pte_t *walk_page_table(unsigned long addr)
static void change_page_attr(unsigned long addr, int numpages,
pte_t (*set) (pte_t))
{
- pte_t *ptep, pte;
+ pte_t *ptep;
int i;
for (i = 0; i < numpages; i++) {
ptep = walk_page_table(addr);
if (WARN_ON_ONCE(!ptep))
break;
- pte = *ptep;
- pte = set(pte);
- __ptep_ipte(addr, ptep);
- *ptep = pte;
+ *ptep = set(*ptep);
addr += PAGE_SIZE;
}
+ __tlb_flush_kernel();
}
int set_memory_ro(unsigned long addr, int numpages)
--
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