userfaultfd: hugetlbfs: prevent UFFDIO_COPY to fill beyond the end of i_size
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/20171016223914.2421-2-aarcange@redhat.comSigned-off-by: NAndrea Arcangeli <aarcange@redhat.com> Reviewed-by: NMike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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