From 24be02a42181f0707be0498045c4c4b13273b16d Mon Sep 17 00:00:00 2001 From: ZhangPeng Date: Wed, 13 Mar 2024 09:29:13 +0800 Subject: [PATCH] filemap: replace pte_offset_map() with pte_offset_map_nolock() 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@huawei.com Fixes: 58f327f2ce80 ("filemap: avoid unnecessary major faults in filemap_fault()") Signed-off-by: ZhangPeng Suggested-by: David Hildenbrand Reviewed-by: David Hildenbrand Cc: Aneesh Kumar K.V Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Kefeng Wang Cc: Matthew Wilcox (Oracle) Cc: Nanyong Sun Cc: Yang Shi Cc: Yin Fengwei Cc: Signed-off-by: Andrew Morton --- mm/filemap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/filemap.c b/mm/filemap.c index 298485d4b9927..657bcd887fdb8 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3231,7 +3231,8 @@ static vm_fault_t filemap_fault_recheck_pte_none(struct vm_fault *vmf) 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; -- 2.50.1