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s390/mm,ptdump: hold cpa mutex while walking for kernel page table dump

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This is currently only preventing that outdated information is
provided to user space. A concurrent split of huge/large pages does
modify the kernel page tables, however either the huge/large mapping
is reported or the split area is being walked.

This "fixes" also only a potential future bug, since split pages could
also be merged again if page permissions are the same for larger
memory areas.

Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2020-09-07 17:20:05 +02:00 committed by Vasily Gorbik
parent 36c2733c43
commit da1694ad9e
3 changed files with 8 additions and 1 deletions
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4
arch/s390/include/asm/set_memory.h
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@ -2,6 +2,10 @@
#ifndef _ASMS390_SET_MEMORY_H #ifndef _ASMS390_SET_MEMORY_H
#define _ASMS390_SET_MEMORY_H #define _ASMS390_SET_MEMORY_H
#include <linux/mutex.h>
extern struct mutex cpa_mutex;
#define SET_MEMORY_RO 1UL #define SET_MEMORY_RO 1UL
#define SET_MEMORY_RW 2UL #define SET_MEMORY_RW 2UL
#define SET_MEMORY_NX 4UL #define SET_MEMORY_NX 4UL

3
arch/s390/mm/dump_pagetables.c
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@ -1,4 +1,5 @@
// SPDX-License-Identifier: GPL-2.0 // SPDX-License-Identifier: GPL-2.0
#include <linux/set_memory.h>
#include <linux/ptdump.h> #include <linux/ptdump.h>
#include <linux/seq_file.h> #include <linux/seq_file.h>
#include <linux/debugfs.h> #include <linux/debugfs.h>
@ -130,7 +131,9 @@ static int ptdump_show(struct seq_file *m, void *v)
}; };
get_online_mems(); get_online_mems();
mutex_lock(&cpa_mutex);
ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
mutex_unlock(&cpa_mutex);
put_online_mems(); put_online_mems();
return 0; return 0;
} }

2
arch/s390/mm/pageattr.c
View File

@ -278,7 +278,7 @@ static int walk_p4d_level(pgd_t *pgd, unsigned long addr, unsigned long end,
return rc; return rc;
} }
static DEFINE_MUTEX(cpa_mutex); DEFINE_MUTEX(cpa_mutex);
static int change_page_attr(unsigned long addr, unsigned long end, static int change_page_attr(unsigned long addr, unsigned long end,
unsigned long flags) unsigned long flags)