Commit 0f6f281b authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

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



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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 8143adaf

arch/s390/include/asm/mmu_context.h

+13 −1
Original line number Diff line number Diff line
@@ -11,7 +11,6 @@ 
#include <asm/uaccess.h>

#include <asm/tlbflush.h>

#include <asm/ctl_reg.h>

#include <asm-generic/mm_hooks.h>



static inline int init_new_context(struct task_struct *tsk,

				   struct mm_struct *mm)
@@ -91,4 +90,17 @@ static inline void activate_mm(struct mm_struct *prev, 
        switch_mm(prev, next, current);

}



static inline void arch_dup_mmap(struct mm_struct *oldmm,

				 struct mm_struct *mm)

{

#ifdef CONFIG_64BIT

	if (oldmm->context.asce_limit < mm->context.asce_limit)

		crst_table_downgrade(mm, oldmm->context.asce_limit);

#endif

}



static inline void arch_exit_mmap(struct mm_struct *mm)

{

}



#endif /* __S390_MMU_CONTEXT_H */

arch/s390/include/asm/processor.h

+2 −0
Original line number Diff line number Diff line
@@ -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 */

arch/s390/mm/mmap.c

+10 −2
Original line number Diff line number Diff line
@@ -103,9 +103,15 @@ void arch_pick_mmap_layout(struct mm_struct *mm) 


int s390_mmap_check(unsigned long addr, unsigned long len)

{

	int rc;



	if (!is_compat_task() &&

	    len >= TASK_SIZE && TASK_SIZE < (1UL << 53))

		return crst_table_upgrade(current->mm, 1UL << 53);

	    len >= TASK_SIZE && TASK_SIZE < (1UL << 53)) {

		rc = crst_table_upgrade(current->mm, 1UL << 53);

		if (rc)

			return rc;

		update_mm(current->mm, current);

	}

	return 0;

}
@@ -125,6 +131,7 @@ s390_get_unmapped_area(struct file *filp, unsigned long addr, 
		rc = crst_table_upgrade(mm, 1UL << 53);

		if (rc)

			return (unsigned long) rc;

		update_mm(mm, current);

		area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);

	}

	return area;
@@ -147,6 +154,7 @@ s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr, 
		rc = crst_table_upgrade(mm, 1UL << 53);

		if (rc)

			return (unsigned long) rc;

		update_mm(mm, current);

		area = arch_get_unmapped_area_topdown(filp, addr, len,

						      pgoff, flags);

	}

arch/s390/mm/pgtable.c

+0 −5
Original line number Diff line number Diff line
@@ -85,7 +85,6 @@ repeat: 
		crst_table_free(mm, table);

	if (mm->context.asce_limit < limit)

		goto repeat;

	update_mm(mm, current);

	return 0;

}
@@ -93,9 +92,6 @@ void crst_table_downgrade(struct mm_struct *mm, unsigned long limit) 
{

	pgd_t *pgd;



	if (mm->context.asce_limit <= limit)

		return;

	__tlb_flush_mm(mm);

	while (mm->context.asce_limit > limit) {

		pgd = mm->pgd;

		switch (pgd_val(*pgd) & _REGION_ENTRY_TYPE_MASK) {
@@ -118,7 +114,6 @@ void crst_table_downgrade(struct mm_struct *mm, unsigned long limit) 
		mm->task_size = mm->context.asce_limit;

		crst_table_free(mm, (unsigned long *) pgd);

	}

	update_mm(mm, current);

}

#endif

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