4.13-stable review patch. If anyone has any objections, please let me know.
------------------ From: Andrea Arcangeli <[email protected]> commit 1e3921471354244f70fe268586ff94a97a6dd4df upstream. This oops: kernel BUG at fs/hugetlbfs/inode.c:484! RIP: remove_inode_hugepages+0x3d0/0x410 Call Trace: hugetlbfs_setattr+0xd9/0x130 notify_change+0x292/0x410 do_truncate+0x65/0xa0 do_sys_ftruncate.constprop.3+0x11a/0x180 SyS_ftruncate+0xe/0x10 tracesys+0xd9/0xde was caused by the lack of i_size check in hugetlb_mcopy_atomic_pte. mmap() can still succeed beyond the end of the i_size after vmtruncate zapped vmas in those ranges, but the faults must not succeed, and that includes UFFDIO_COPY. We could differentiate the retval to userland to represent a SIGBUS like a page fault would do (vs SIGSEGV), but it doesn't seem very useful and we'd need to pick a random retval as there's no meaningful syscall retval that would differentiate from SIGSEGV and SIGBUS, there's just -EFAULT. Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Andrea Arcangeli <[email protected]> Reviewed-by: Mike Kravetz <[email protected]> Cc: Mike Rapoport <[email protected]> Cc: "Dr. David Alan Gilbert" <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- mm/hugetlb.c | 32 ++++++++++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3977,6 +3977,9 @@ int hugetlb_mcopy_atomic_pte(struct mm_s unsigned long src_addr, struct page **pagep) { + struct address_space *mapping; + pgoff_t idx; + unsigned long size; int vm_shared = dst_vma->vm_flags & VM_SHARED; struct hstate *h = hstate_vma(dst_vma); pte_t _dst_pte; @@ -4014,13 +4017,24 @@ int hugetlb_mcopy_atomic_pte(struct mm_s __SetPageUptodate(page); set_page_huge_active(page); + mapping = dst_vma->vm_file->f_mapping; + idx = vma_hugecache_offset(h, dst_vma, dst_addr); + /* * If shared, add to page cache */ if (vm_shared) { - struct address_space *mapping = dst_vma->vm_file->f_mapping; - pgoff_t idx = vma_hugecache_offset(h, dst_vma, dst_addr); + size = i_size_read(mapping->host) >> huge_page_shift(h); + ret = -EFAULT; + if (idx >= size) + goto out_release_nounlock; + /* + * Serialization between remove_inode_hugepages() and + * huge_add_to_page_cache() below happens through the + * hugetlb_fault_mutex_table that here must be hold by + * the caller. + */ ret = huge_add_to_page_cache(page, mapping, idx); if (ret) goto out_release_nounlock; @@ -4029,6 +4043,20 @@ int hugetlb_mcopy_atomic_pte(struct mm_s ptl = huge_pte_lockptr(h, dst_mm, dst_pte); spin_lock(ptl); + /* + * Recheck the i_size after holding PT lock to make sure not + * to leave any page mapped (as page_mapped()) beyond the end + * of the i_size (remove_inode_hugepages() is strict about + * enforcing that). If we bail out here, we'll also leave a + * page in the radix tree in the vm_shared case beyond the end + * of the i_size, but remove_inode_hugepages() will take care + * of it as soon as we drop the hugetlb_fault_mutex_table. + */ + size = i_size_read(mapping->host) >> huge_page_shift(h); + ret = -EFAULT; + if (idx >= size) + goto out_release_unlock; + ret = -EEXIST; if (!huge_pte_none(huge_ptep_get(dst_pte))) goto out_release_unlock;
