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s390/mm: fix vunmap vs finish_arch_post_lock_switch

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The vunmap_pte_range() function calls ptep_get_and_clear() without any
locking. ptep_get_and_clear() uses ptep_xchg_lazy()/ptep_flush_direct()
for the page table update. ptep_flush_direct requires that preemption
is disabled, but without any locking this is not the case. If the kernel
preempts the task while the attach_counter is increased an endless loop
in finish_arch_post_lock_switch() will occur the next time the task is
scheduled.

Add explicit preempt_disable()/preempt_enable() calls to the relevant
functions in arch/s390/mm/pgtable.c.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2016-06-06 10:30:45 +02:00
parent fd5ada0403
commit a9809407f6
1 changed files with 18 additions and 2 deletions
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20
arch/s390/mm/pgtable.c
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@ -70,7 +70,6 @@ static inline pgste_t pgste_get_lock(pte_t *ptep)
#ifdef CONFIG_PGSTE
unsigned long old;
preempt_disable();
asm(
" lg %0,%2\n"
"0: lgr %1,%0\n"
@ -93,7 +92,6 @@ static inline void pgste_set_unlock(pte_t *ptep, pgste_t pgste)
: "=Q" (ptep[PTRS_PER_PTE])
: "d" (pgste_val(pgste)), "Q" (ptep[PTRS_PER_PTE])
: "cc", "memory");
preempt_enable();
#endif
}
@ -230,9 +228,11 @@ pte_t ptep_xchg_direct(struct mm_struct *mm, unsigned long addr,
pgste_t pgste;
pte_t old;
preempt_disable();
pgste = ptep_xchg_start(mm, addr, ptep);
old = ptep_flush_direct(mm, addr, ptep);
ptep_xchg_commit(mm, addr, ptep, pgste, old, new);
preempt_enable();
return old;
}
EXPORT_SYMBOL(ptep_xchg_direct);
@ -243,9 +243,11 @@ pte_t ptep_xchg_lazy(struct mm_struct *mm, unsigned long addr,
pgste_t pgste;
pte_t old;
preempt_disable();
pgste = ptep_xchg_start(mm, addr, ptep);
old = ptep_flush_lazy(mm, addr, ptep);
ptep_xchg_commit(mm, addr, ptep, pgste, old, new);
preempt_enable();
return old;
}
EXPORT_SYMBOL(ptep_xchg_lazy);
@ -256,6 +258,7 @@ pte_t ptep_modify_prot_start(struct mm_struct *mm, unsigned long addr,
pgste_t pgste;
pte_t old;
preempt_disable();
pgste = ptep_xchg_start(mm, addr, ptep);
old = ptep_flush_lazy(mm, addr, ptep);
if (mm_has_pgste(mm)) {
@ -279,6 +282,7 @@ void ptep_modify_prot_commit(struct mm_struct *mm, unsigned long addr,
} else {
*ptep = pte;
}
preempt_enable();
}
EXPORT_SYMBOL(ptep_modify_prot_commit);
@ -333,8 +337,10 @@ pmd_t pmdp_xchg_direct(struct mm_struct *mm, unsigned long addr,
{
pmd_t old;
preempt_disable();
old = pmdp_flush_direct(mm, addr, pmdp);
*pmdp = new;
preempt_enable();
return old;
}
EXPORT_SYMBOL(pmdp_xchg_direct);
@ -344,8 +350,10 @@ pmd_t pmdp_xchg_lazy(struct mm_struct *mm, unsigned long addr,
{
pmd_t old;
preempt_disable();
old = pmdp_flush_lazy(mm, addr, pmdp);
*pmdp = new;
preempt_enable();
return old;
}
EXPORT_SYMBOL(pmdp_xchg_lazy);
@ -398,20 +406,24 @@ void ptep_set_pte_at(struct mm_struct *mm, unsigned long addr,
pgste_t pgste;
/* the mm_has_pgste() check is done in set_pte_at() */
preempt_disable();
pgste = pgste_get_lock(ptep);
pgste_val(pgste) &= ~_PGSTE_GPS_ZERO;
pgste_set_key(ptep, pgste, entry, mm);
pgste = pgste_set_pte(ptep, pgste, entry);
pgste_set_unlock(ptep, pgste);
preempt_enable();
}
void ptep_set_notify(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
{
pgste_t pgste;
preempt_disable();
pgste = pgste_get_lock(ptep);
pgste_val(pgste) |= PGSTE_IN_BIT;
pgste_set_unlock(ptep, pgste);
preempt_enable();
}
static void ptep_zap_swap_entry(struct mm_struct *mm, swp_entry_t entry)
@ -434,6 +446,7 @@ void ptep_zap_unused(struct mm_struct *mm, unsigned long addr,
pte_t pte;
/* Zap unused and logically-zero pages */
preempt_disable();
pgste = pgste_get_lock(ptep);
pgstev = pgste_val(pgste);
pte = *ptep;
@ -446,6 +459,7 @@ void ptep_zap_unused(struct mm_struct *mm, unsigned long addr,
if (reset)
pgste_val(pgste) &= ~_PGSTE_GPS_USAGE_MASK;
pgste_set_unlock(ptep, pgste);
preempt_enable();
}
void ptep_zap_key(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
@ -454,6 +468,7 @@ void ptep_zap_key(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
pgste_t pgste;
/* Clear storage key */
preempt_disable();
pgste = pgste_get_lock(ptep);
pgste_val(pgste) &= ~(PGSTE_ACC_BITS | PGSTE_FP_BIT |
PGSTE_GR_BIT | PGSTE_GC_BIT);
@ -461,6 +476,7 @@ void ptep_zap_key(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
if (!(ptev & _PAGE_INVALID) && (ptev & _PAGE_WRITE))
page_set_storage_key(ptev & PAGE_MASK, PAGE_DEFAULT_KEY, 1);
pgste_set_unlock(ptep, pgste);
preempt_enable();
}
/*