• Dan Williams's avatar
    x86/asm/memcpy_mcsafe: Fix copy_to_user_mcsafe() exception handling · 092b31aa
    Dan Williams authored
    All copy_to_user() implementations need to be prepared to handle faults
    accessing userspace. The __memcpy_mcsafe() implementation handles both
    mmu-faults on the user destination and machine-check-exceptions on the
    source buffer. However, the memcpy_mcsafe() wrapper may silently
    fallback to memcpy() depending on build options and cpu-capabilities.
    
    Force copy_to_user_mcsafe() to always use __memcpy_mcsafe() when
    available, and otherwise disable all of the copy_to_user_mcsafe()
    infrastructure when __memcpy_mcsafe() is not available, i.e.
    CONFIG_X86_MCE=n.
    
    This fixes crashes of the form:
        run fstests generic/323 at 2018-07-02 12:46:23
        BUG: unable to handle kernel paging request at 00007f0d50001000
        RIP: 0010:__memcpy+0x12/0x20
        [..]
        Call Trace:
         copyout_mcsafe+0x3a/0x50
         _copy_to_iter_mcsafe+0xa1/0x4a0
         ? dax_alive+0x30/0x50
         dax_iomap_actor+0x1f9/0x280
         ? dax_iomap_rw+0x100/0x100
         iomap_apply+0xba/0x130
         ? dax_iomap_rw+0x100/0x100
         dax_iomap_rw+0x95/0x100
         ? dax_iomap_rw+0x100/0x100
         xfs_file_dax_read+0x7b/0x1d0 [xfs]
         xfs_file_read_iter+0xa7/0xc0 [xfs]
         aio_read+0x11c/0x1a0
    Reported-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
    Tested-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
    Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Tony Luck <tony.luck@intel.com>
    Fixes: 8780356e ("x86/asm/memcpy_mcsafe: Define copy_to_iter_mcsafe()")
    Link: http://lkml.kernel.org/r/153108277790.37979.1486841789275803399.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    092b31aa
uaccess_64.h 5.78 KB