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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2019-01-08 12:44:57 +0100 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2019-01-11 17:12:02 +0100 |
| commit | a38662084c8bdb829ff486468c7ea801c13fcc34 (patch) | |
| tree | 43557879c0695fdada5b9c95b849e11ce2b48f9d /arch/s390 | |
| parent | 03aa047ef2db4985e444af6ee1c1dd084ad9fb4c (diff) | |
| download | linux-a38662084c8bdb829ff486468c7ea801c13fcc34.tar.bz2 | |
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This can lead to a situation where a CPU uses the outdated ASCE to run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/s390')
| -rw-r--r-- | arch/s390/include/asm/mmu_context.h | 5 |
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 |