[PATCH 6.9 089/143] filemap: replace pte_offset_map() with pte_offset_map_nolock()

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

------------------

From: ZhangPeng <zhangpeng362@xxxxxxxxxx>

commit 24be02a42181f0707be0498045c4c4b13273b16d upstream.

The vmf->ptl in filemap_fault_recheck_pte_none() is still set from
handle_pte_fault().  But at the same time, we did a pte_unmap(vmf->pte).
After a pte_unmap(vmf->pte) unmap and rcu_read_unlock(), the page table
may be racily changed and vmf->ptl maybe fails to protect the actual page
table.  Fix this by replacing pte_offset_map() with
pte_offset_map_nolock().

As David said, the PTL pointer might be stale so if we continue to use
it infilemap_fault_recheck_pte_none(), it might trigger UAF.  Also, if
the PTL fails, the issue fixed by commit 58f327f2ce80 ("filemap: avoid
unnecessary major faults in filemap_fault()") might reappear.

Link: https://lkml.kernel.org/r/20240313012913.2395414-1-zhangpeng362@xxxxxxxxxx
Fixes: 58f327f2ce80 ("filemap: avoid unnecessary major faults in filemap_fault()")
Signed-off-by: ZhangPeng <zhangpeng362@xxxxxxxxxx>
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Nanyong Sun <sunnanyong@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 mm/filemap.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3207,7 +3207,8 @@ static vm_fault_t filemap_fault_recheck_
 	if (!(vmf->flags & FAULT_FLAG_ORIG_PTE_VALID))
 		return 0;
 
-	ptep = pte_offset_map(vmf->pmd, vmf->address);
+	ptep = pte_offset_map_nolock(vma->vm_mm, vmf->pmd, vmf->address,
+				     &vmf->ptl);
 	if (unlikely(!ptep))
 		return VM_FAULT_NOPAGE;
 






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