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[GIT,PULL,02/17] s390/gmap: don't unconditionally call pte_unmap_unlock() in __gmap_zap()

Message ID 20211031121104.14764-3-borntraeger@de.ibm.com (mailing list archive)
State New, archived
Headers show
Series [GIT,PULL,01/17] s390/gmap: validate VMA in __gmap_zap() | expand

Commit Message

Christian Borntraeger Oct. 31, 2021, 12:10 p.m. UTC 
From: David Hildenbrand <david@redhat.com>

... otherwise we will try unlocking a spinlock that was never locked via a
garbage pointer.

At the time we reach this code path, we usually successfully looked up
a PGSTE already; however, evil user space could have manipulated the VMA
layout in the meantime and triggered removal of the page table.

Fixes: 1e133ab296f3 ("s390/mm: split arch/s390/mm/pgtable.c")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Link: https://lore.kernel.org/r/20210909162248.14969-3-david@redhat.com
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 arch/s390/mm/gmap.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
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Patch

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index e0735c343775..d63c0ccc5ccd 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -689,9 +689,10 @@  void __gmap_zap(struct gmap *gmap, unsigned long gaddr)
 
 		/* Get pointer to the page table entry */
 		ptep = get_locked_pte(gmap->mm, vmaddr, &ptl);
-		if (likely(ptep))
+		if (likely(ptep)) {
 			ptep_zap_unused(gmap->mm, vmaddr, ptep, 0);
-		pte_unmap_unlock(ptep, ptl);
+			pte_unmap_unlock(ptep, ptl);
+		}
 	}
 }
 EXPORT_SYMBOL_GPL(__gmap_zap);