diff options
Diffstat (limited to 'mm/memory.c')
| -rw-r--r-- | mm/memory.c | 28 |
1 files changed, 16 insertions, 12 deletions
diff --git a/mm/memory.c b/mm/memory.c index 01f39e8144ef..603b2f419948 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5393,27 +5393,28 @@ retry: if (!vma_is_anonymous(vma) && !vma_is_tcp(vma)) goto inval; - /* find_mergeable_anon_vma uses adjacent vmas which are not locked */ - if (!vma->anon_vma && !vma_is_tcp(vma)) - goto inval; - if (!vma_start_read(vma)) goto inval; /* + * find_mergeable_anon_vma uses adjacent vmas which are not locked. + * This check must happen after vma_start_read(); otherwise, a + * concurrent mremap() with MREMAP_DONTUNMAP could dissociate the VMA + * from its anon_vma. + */ + if (unlikely(!vma->anon_vma && !vma_is_tcp(vma))) + goto inval_end_read; + + /* * Due to the possibility of userfault handler dropping mmap_lock, avoid * it for now and fall back to page fault handling under mmap_lock. */ - if (userfaultfd_armed(vma)) { - vma_end_read(vma); - goto inval; - } + if (userfaultfd_armed(vma)) + goto inval_end_read; /* Check since vm_start/vm_end might change before we lock the VMA */ - if (unlikely(address < vma->vm_start || address >= vma->vm_end)) { - vma_end_read(vma); - goto inval; - } + if (unlikely(address < vma->vm_start || address >= vma->vm_end)) + goto inval_end_read; /* Check if the VMA got isolated after we found it */ if (vma->detached) { @@ -5425,6 +5426,9 @@ retry: rcu_read_unlock(); return vma; + +inval_end_read: + vma_end_read(vma); inval: rcu_read_unlock(); count_vm_vma_lock_event(VMA_LOCK_ABORT); |