s390/mm: fix gmap tlb flush issues

commit f045402984404ddc11016358411e445192919047 upstream.

__tlb_flush_asce() should never be used if multiple asce belong to a mm.

As this function changes mm logic determining if local or global tlb
flushes will be neded, we might end up flushing only the gmap asce on all
CPUs and a follow up mm asce flushes will only flush on the local CPU,
although that asce ran on multiple CPUs.

The missing tlb flushes will provoke strange faults in user space and even
low address protections in user space, crashing the kernel.

Fixes: 1b948d6caec4 ("s390/mm,tlb: optimize TLB flushing for zEC12")
Cc: stable@vger.kernel.org # 3.15+
Reported-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/s390/include/asm/tlbflush.h b/arch/s390/include/asm/tlbflush.h
index a2e6ef32e05445b190b444cb249db44f638e10d2..0a2031618f7fc619326c3d3e69f20dd71802c4dd 100644 (file)
--- a/arch/s390/include/asm/tlbflush.h
+++ b/arch/s390/include/asm/tlbflush.h
@@ -81,7 +81,8 @@ static inline void __tlb_flush_full(struct mm_struct *mm)
 }
 
 /*
- * Flush TLB entries for a specific ASCE on all CPUs.
+ * Flush TLB entries for a specific ASCE on all CPUs. Should never be used
+ * when more than one asce (e.g. gmap) ran on this mm.
  */
 static inline void __tlb_flush_asce(struct mm_struct *mm, unsigned long asce)
 {

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 471a370a527bfd9eb5e9bd03e98a9e6c7eff4b96..8345ae1f117d0cfdf4cfcadc5a01c0ec4bfd7174 100644 (file)
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -166,7 +166,7 @@ EXPORT_SYMBOL_GPL(gmap_alloc);
 static void gmap_flush_tlb(struct gmap *gmap)
 {
        if (MACHINE_HAS_IDTE)
-               __tlb_flush_asce(gmap->mm, gmap->asce);
+               __tlb_flush_idte(gmap->asce);
        else
                __tlb_flush_global();
 }
@@ -205,7 +205,7 @@ void gmap_free(struct gmap *gmap)
 
        /* Flush tlb. */
        if (MACHINE_HAS_IDTE)
-               __tlb_flush_asce(gmap->mm, gmap->asce);
+               __tlb_flush_idte(gmap->asce);
        else
                __tlb_flush_global();