From: David Hildenbrand david@redhat.com
[ Upstream commit 1493e0f944f3c319d11e067c185c904d01c17ae5 ]
We have to properly retry again by returning -EINVAL immediately in case somebody else instantiated the table concurrently. We missed to add the goto in this function only. The code now matches the other, similar shadowing functions.
We are overwriting an existing region 2 table entry. All allocated pages are added to the crst_list to be freed later, so they are not lost forever. However, when unshadowing the region 2 table, we wouldn't trigger unshadowing of the original shadowed region 3 table that we replaced. It would get unshadowed when the original region 3 table is modified. As it's not connected to the page table hierarchy anymore, it's not going to get used anymore. However, for a limited time, this page table will stick around, so it's in some sense a temporary memory leak.
Identified by manual code inspection. I don't think this classifies as stable material.
Fixes: 998f637cc4b9 ("s390/mm: avoid races on region/segment/page table shadowing") Signed-off-by: David Hildenbrand david@redhat.com Link: https://lore.kernel.org/r/20200403153050.20569-4-david@redhat.com Reviewed-by: Claudio Imbrenda imbrenda@linux.ibm.com Reviewed-by: Christian Borntraeger borntraeger@de.ibm.com Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/mm/gmap.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c index edcdca97e85ee..06d602c5ec7b7 100644 --- a/arch/s390/mm/gmap.c +++ b/arch/s390/mm/gmap.c @@ -1840,6 +1840,7 @@ int gmap_shadow_r3t(struct gmap *sg, unsigned long saddr, unsigned long r3t, goto out_free; } else if (*table & _REGION_ENTRY_ORIGIN) { rc = -EAGAIN; /* Race with shadow */ + goto out_free; } crst_table_init(s_r3t, _REGION3_ENTRY_EMPTY); /* mark as invalid as long as the parent table is not protected */