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s390/mm: downgrade page table after fork of a 31 bit process

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The downgrade of the 4 level page table created by init_new_context is
currently done only in start_thread31. If a 31 bit process forks the
new mm uses a 4 level page table, including the task size of 2<<42
that goes along with it. This is incorrect as now a 31 bit process
can map memory beyond 2GB. Define arch_dup_mmap to do the downgrade
after fork.

Cc: stable@vger.kernel.org
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky
2012-07-26 08:53:06 +02:00
parent 8143adafd2
commit 0f6f281b73
4 changed files with 25 additions and 8 deletions
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arch/s390/include/asm/processor.h
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@@ -120,7 +120,9 @@ struct stack_frame {
regs->psw.mask = psw_user_bits | PSW_MASK_BA; \
regs->psw.addr = new_psw | PSW_ADDR_AMODE; \
regs->gprs[15] = new_stackp; \
__tlb_flush_mm(current->mm); \
crst_table_downgrade(current->mm, 1UL << 31); \
update_mm(current->mm, current); \
} while (0)
/* Forward declaration, a strange C thing */