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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2019-01-08 12:44:57 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2019-01-11 17:12:02 +0100
commita38662084c8bdb829ff486468c7ea801c13fcc34 (patch)
tree43557879c0695fdada5b9c95b849e11ce2b48f9d /arch
parent03aa047ef2db4985e444af6ee1c1dd084ad9fb4c (diff)
s390/mm: always force a load of the primary ASCE on context switch
The ASCE of an mm_struct can be modified after a task has been created, e.g. via crst_table_downgrade for a compat process. The active_mm logic to avoid the switch_mm call if the next task is a kernel thread can lead to a situation where switch_mm is called where 'prev == next' is true but 'prev->context.asce == next->context.asce' is not. This can lead to a situation where a CPU uses the outdated ASCE to run a task. The result can be a crash, endless loops and really subtle problem due to TLBs being created with an invalid ASCE. Cc: stable@kernel.org # v3.15+ Fixes: 53e857f30867 ("s390/mm,tlb: race of lazy TLB flush vs. recreation") Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com> Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/s390/include/asm/mmu_context.h5
1 files changed, 2 insertions, 3 deletions
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index ccbb53e22024..e4462202200d 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -90,8 +90,6 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
{
int cpu = smp_processor_id();
- if (prev == next)
- return;
S390_lowcore.user_asce = next->context.asce;
cpumask_set_cpu(cpu, &next->context.cpu_attach_mask);
/* Clear previous user-ASCE from CR1 and CR7 */
@@ -103,7 +101,8 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
__ctl_load(S390_lowcore.vdso_asce, 7, 7);
clear_cpu_flag(CIF_ASCE_SECONDARY);
}
- cpumask_clear_cpu(cpu, &prev->context.cpu_attach_mask);
+ if (prev != next)
+ cpumask_clear_cpu(cpu, &prev->context.cpu_attach_mask);
}
#define finish_arch_post_lock_switch finish_arch_post_lock_switch