The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Possible dependencies:
958f32ce832b ("mm: hugetlb: fix UAF in hugetlb_handle_userfault") 40549ba8f8e0 ("hugetlb: use new vma_lock for pmd sharing synchronization") 378397ccb8e5 ("hugetlb: create hugetlb_unmap_file_folio to unmap single file folio") 8d9bfb260814 ("hugetlb: add vma based lock for pmd sharing") 12710fd69634 ("hugetlb: rename vma_shareable() and refactor code") c86272287bc6 ("hugetlb: create remove_inode_single_folio to remove single file folio") 7e1813d48dd3 ("hugetlb: rename remove_huge_page to hugetlb_delete_from_page_cache") 3a47c54f09c4 ("hugetlbfs: revert use i_mmap_rwsem for more pmd sharing synchronization") 188a39725ad7 ("hugetlbfs: revert use i_mmap_rwsem to address page fault/truncate race") 5e6b1bf1b5c3 ("hugetlb: remove meaningless BUG_ON(huge_pte_none())") 3a5497a2dae3 ("mm/hugetlb: fix missing call to restore_reserve_on_error()") 6614a3c3164a ("Merge tag 'mm-stable-2022-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 958f32ce832ba781ac20e11bb2d12a9352ea28fc Mon Sep 17 00:00:00 2001 From: Liu Shixin liushixin2@huawei.com Date: Fri, 23 Sep 2022 12:21:13 +0800 Subject: [PATCH] mm: hugetlb: fix UAF in hugetlb_handle_userfault
The vma_lock and hugetlb_fault_mutex are dropped before handling userfault and reacquire them again after handle_userfault(), but reacquire the vma_lock could lead to UAF[1,2] due to the following race,
hugetlb_fault hugetlb_no_page /*unlock vma_lock */ hugetlb_handle_userfault handle_userfault /* unlock mm->mmap_lock*/ vm_mmap_pgoff do_mmap mmap_region munmap_vma_range /* clean old vma */ /* lock vma_lock again <--- UAF */ /* unlock vma_lock */
Since the vma_lock will unlock immediately after hugetlb_handle_userfault(), let's drop the unneeded lock and unlock in hugetlb_handle_userfault() to fix the issue.
[1] https://lore.kernel.org/linux-mm/000000000000d5e00a05e834962e@google.com/ [2] https://lore.kernel.org/linux-mm/20220921014457.1668-1-liuzixian4@huawei.com... Link: https://lkml.kernel.org/r/20220923042113.137273-1-liushixin2@huawei.com Fixes: 1a1aad8a9b7b ("userfaultfd: hugetlbfs: add userfaultfd hugetlb hook") Signed-off-by: Liu Shixin liushixin2@huawei.com Signed-off-by: Kefeng Wang wangkefeng.wang@huawei.com Reported-by: syzbot+193f9cee8638750b23cf@syzkaller.appspotmail.com Reported-by: Liu Zixian liuzixian4@huawei.com Reviewed-by: Mike Kravetz mike.kravetz@oracle.com Cc: David Hildenbrand david@redhat.com Cc: John Hubbard jhubbard@nvidia.com Cc: Muchun Song songmuchun@bytedance.com Cc: Sidhartha Kumar sidhartha.kumar@oracle.com Cc: stable@vger.kernel.org [4.14+] Signed-off-by: Andrew Morton akpm@linux-foundation.org
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 2182134216f0..3c1316ad54b5 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5489,7 +5489,6 @@ static inline vm_fault_t hugetlb_handle_userfault(struct vm_area_struct *vma, unsigned long addr, unsigned long reason) { - vm_fault_t ret; u32 hash; struct vm_fault vmf = { .vma = vma, @@ -5507,18 +5506,14 @@ static inline vm_fault_t hugetlb_handle_userfault(struct vm_area_struct *vma, };
/* - * vma_lock and hugetlb_fault_mutex must be - * dropped before handling userfault. Reacquire - * after handling fault to make calling code simpler. + * vma_lock and hugetlb_fault_mutex must be dropped before handling + * userfault. Also mmap_lock could be dropped due to handling + * userfault, any vma operation should be careful from here. */ hugetlb_vma_unlock_read(vma); hash = hugetlb_fault_mutex_hash(mapping, idx); mutex_unlock(&hugetlb_fault_mutex_table[hash]); - ret = handle_userfault(&vmf, reason); - mutex_lock(&hugetlb_fault_mutex_table[hash]); - hugetlb_vma_lock_read(vma); - - return ret; + return handle_userfault(&vmf, reason); }
static vm_fault_t hugetlb_no_page(struct mm_struct *mm, @@ -5536,6 +5531,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, spinlock_t *ptl; unsigned long haddr = address & huge_page_mask(h); bool new_page, new_pagecache_page = false; + u32 hash = hugetlb_fault_mutex_hash(mapping, idx);
/* * Currently, we are forced to kill the process in the event the @@ -5546,7 +5542,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, if (is_vma_resv_set(vma, HPAGE_RESV_UNMAPPED)) { pr_warn_ratelimited("PID %d killed due to inadequate hugepage pool\n", current->pid); - return ret; + goto out; }
/* @@ -5560,12 +5556,10 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, if (idx >= size) goto out; /* Check for page in userfault range */ - if (userfaultfd_missing(vma)) { - ret = hugetlb_handle_userfault(vma, mapping, idx, + if (userfaultfd_missing(vma)) + return hugetlb_handle_userfault(vma, mapping, idx, flags, haddr, address, VM_UFFD_MISSING); - goto out; - }
page = alloc_huge_page(vma, haddr, 0); if (IS_ERR(page)) { @@ -5631,10 +5625,9 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, if (userfaultfd_minor(vma)) { unlock_page(page); put_page(page); - ret = hugetlb_handle_userfault(vma, mapping, idx, + return hugetlb_handle_userfault(vma, mapping, idx, flags, haddr, address, VM_UFFD_MINOR); - goto out; } }
@@ -5692,6 +5685,8 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
unlock_page(page); out: + hugetlb_vma_unlock_read(vma); + mutex_unlock(&hugetlb_fault_mutex_table[hash]); return ret;
backout: @@ -5789,11 +5784,13 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
entry = huge_ptep_get(ptep); /* PTE markers should be handled the same way as none pte */ - if (huge_pte_none_mostly(entry)) { - ret = hugetlb_no_page(mm, vma, mapping, idx, address, ptep, + if (huge_pte_none_mostly(entry)) + /* + * hugetlb_no_page will drop vma lock and hugetlb fault + * mutex internally, which make us return immediately. + */ + return hugetlb_no_page(mm, vma, mapping, idx, address, ptep, entry, flags); - goto out_mutex; - }
ret = 0;