• Jan Kara's avatar
    mm: Preserve _PAGE_DEVMAP across mprotect() calls · 1b7ff520
    Jan Kara authored
    commit 4628a645 upstream.
    
    Currently _PAGE_DEVMAP bit is not preserved in mprotect(2) calls. As a
    result we will see warnings such as:
    
    BUG: Bad page map in process JobWrk0013  pte:800001803875ea25 pmd:7624381067
    addr:00007f0930720000 vm_flags:280000f9 anon_vma:          (null) mapping:ffff97f2384056f0 index:0
    file:457-000000fe00000030-00000009-000000ca-00000001_2001.fileblock fault:xfs_filemap_fault [xfs] mmap:xfs_file_mmap [xfs] readpage:          (null)
    CPU: 3 PID: 15848 Comm: JobWrk0013 Tainted: G        W          4.12.14-2.g7573215-default #1 SLE12-SP4 (unreleased)
    Hardware name: Intel Corporation S2600WFD/S2600WFD, BIOS SE5C620.86B.01.00.0833.051120182255 05/11/2018
    Call Trace:
     dump_stack+0x5a/0x75
     print_bad_pte+0x217/0x2c0
     ? enqueue_task_fair+0x76/0x9f0
     _vm_normal_page+0xe5/0x100
     zap_pte_range+0x148/0x740
     unmap_page_range+0x39a/0x4b0
     unmap_vmas+0x42/0x90
     unmap_region+0x99/0xf0
     ? vma_gap_callbacks_rotate+0x1a/0x20
     do_munmap+0x255/0x3a0
     vm_munmap+0x54/0x80
     SyS_munmap+0x1d/0x30
     do_syscall_64+0x74/0x150
     entry_SYSCALL_64_after_hwframe+0x3d/0xa2
    ...
    
    when mprotect(2) gets used on DAX mappings. Also there is a wide variety
    of other failures that can result from the missing _PAGE_DEVMAP flag
    when the area gets used by get_user_pages() later.
    
    Fix the problem by including _PAGE_DEVMAP in a set of flags that get
    preserved by mprotect(2).
    
    Fixes: 69660fd7 ("x86, mm: introduce _PAGE_DEVMAP")
    Fixes: ebd31197 ("powerpc/mm: Add devmap support for ppc64")
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarJan Kara <jack@suse.cz>
    Acked-by: default avatarMichal Hocko <mhocko@suse.com>
    Reviewed-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
    Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    1b7ff520
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