6.9-stable review patch. If anyone has any objections, please let me know.
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From: ZhangPeng zhangpeng362@huawei.com
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@huawei.com Fixes: 58f327f2ce80 ("filemap: avoid unnecessary major faults in filemap_fault()") Signed-off-by: ZhangPeng zhangpeng362@huawei.com Suggested-by: David Hildenbrand david@redhat.com Reviewed-by: David Hildenbrand david@redhat.com Cc: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Cc: "Huang, Ying" ying.huang@intel.com Cc: Hugh Dickins hughd@google.com Cc: Kefeng Wang wangkefeng.wang@huawei.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Nanyong Sun sunnanyong@huawei.com Cc: Yang Shi shy828301@gmail.com Cc: Yin Fengwei fengwei.yin@intel.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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;