[PATCH 5.0 117/146] mm/memory.c: fix modifying of page protection by insert_pfn()

From: Greg Kroah-Hartman
Date: Mon Apr 01 2019 - 13:10:21 EST

5.0-stable review patch. If anyone has any objections, please let me know.


From: Jan Kara <jack@xxxxxxx>

commit cae85cb8add35f678cf487139d05e083ce2f570a upstream.

Aneesh has reported that PPC triggers the following warning when
excercising DAX code:

IP set_pte_at+0x3c/0x190
LR insert_pfn+0x208/0x280
Call Trace:

Now that is WARN_ON in set_pte_at which is

VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep));

The problem is that on some architectures set_pte_at() cannot cope with
a situation where there is already some (different) valid entry present.

Use ptep_set_access_flags() instead to modify the pfn which is built to
deal with modifying existing PTE.

Link: http://lkml.kernel.org/r/20190311084537.16029-1-jack@xxxxxxx
Fixes: b2770da64254 "mm: add vm_insert_mixed_mkwrite()"
Signed-off-by: Jan Kara <jack@xxxxxxx>
Reported-by: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Acked-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Chandan Rajendra <chandan@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

mm/memory.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1546,10 +1546,12 @@ static vm_fault_t insert_pfn(struct vm_a
goto out_unlock;
- entry = *pte;
- goto out_mkwrite;
- } else
- goto out_unlock;
+ entry = pte_mkyoung(*pte);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ if (ptep_set_access_flags(vma, addr, pte, entry, 1))
+ update_mmu_cache(vma, addr, pte);
+ }
+ goto out_unlock;

/* Ok, finally just insert the thing.. */
@@ -1558,7 +1560,6 @@ static vm_fault_t insert_pfn(struct vm_a
entry = pte_mkspecial(pfn_t_pte(pfn, prot));

if (mkwrite) {
entry = pte_mkyoung(entry);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);