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authorLiu Shixin <liushixin2@huawei.com>2022-09-23 07:21:13 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-10-21 13:39:27 +0300
commit78504bcedb2f1bbfb353b4d233c24d641c4dda33 (patch)
treef0b4d3e2063d898e48b9a8d05c42cd46f137b6c5
parent5156958755853a48de499b330ff9b2a624b463fc (diff)
downloadlinux-78504bcedb2f1bbfb353b4d233c24d641c4dda33.tar.xz
mm: hugetlb: fix UAF in hugetlb_handle_userfault
commit 958f32ce832ba781ac20e11bb2d12a9352ea28fc upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--mm/hugetlb.c37
1 files changed, 17 insertions, 20 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 90dd30c3d949..513b523ba75b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5482,7 +5482,6 @@ 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,
@@ -5500,18 +5499,14 @@ static inline vm_fault_t hugetlb_handle_userfault(struct vm_area_struct *vma,
};
/*
- * hugetlb_fault_mutex and i_mmap_rwsem 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 will be dropped during handling
+ * userfault, any vma operation should be careful from here.
*/
hash = hugetlb_fault_mutex_hash(mapping, idx);
mutex_unlock(&hugetlb_fault_mutex_table[hash]);
i_mmap_unlock_read(mapping);
- ret = handle_userfault(&vmf, reason);
- i_mmap_lock_read(mapping);
- mutex_lock(&hugetlb_fault_mutex_table[hash]);
-
- return ret;
+ return handle_userfault(&vmf, reason);
}
static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
@@ -5529,6 +5524,7 @@ 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
@@ -5539,7 +5535,7 @@ 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;
}
/*
@@ -5556,12 +5552,10 @@ retry:
page = find_lock_page(mapping, idx);
if (!page) {
/* 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)) {
@@ -5621,10 +5615,9 @@ retry:
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;
}
}
@@ -5682,6 +5675,8 @@ retry:
unlock_page(page);
out:
+ mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+ i_mmap_unlock_read(mapping);
return ret;
backout:
@@ -5780,11 +5775,13 @@ 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;