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    x86/pgtable: Don't set huge PUD/PMD on non-leaf entries · e3e28812
    Joerg Roedel 提交于
    The pmd_set_huge() and pud_set_huge() functions are used from
    the generic ioremap() code to establish large mappings where this
    is possible.
    
    But the generic ioremap() code does not check whether the
    PMD/PUD entries are already populated with a non-leaf entry,
    so that any page-table pages these entries point to will be
    lost.
    
    Further, on x86-32 with SHARED_KERNEL_PMD=0, this causes a
    BUG_ON() in vmalloc_sync_one() when PMD entries are synced
    from swapper_pg_dir to the current page-table. This happens
    because the PMD entry from swapper_pg_dir was promoted to a
    huge-page entry while the current PGD still contains the
    non-leaf entry. Because both entries are present and point
    to a different page, the BUG_ON() triggers.
    
    This was actually triggered with pti-x32 enabled in a KVM
    virtual machine by the graphics driver.
    
    A real and better fix for that would be to improve the
    page-table handling in the generic ioremap() code. But that is
    out-of-scope for this patch-set and left for later work.
    Reported-by: NDavid H. Gutteridge <dhgutteridge@sympatico.ca>
    Signed-off-by: NJoerg Roedel <jroedel@suse.de>
    Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: David Laight <David.Laight@aculab.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: Eduardo Valentin <eduval@amazon.com>
    Cc: Greg KH <gregkh@linuxfoundation.org>
    Cc: Jiri Kosina <jkosina@suse.cz>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Juergen Gross <jgross@suse.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Pavel Machek <pavel@ucw.cz>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Waiman Long <llong@redhat.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: aliguori@amazon.com
    Cc: daniel.gruss@iaik.tugraz.at
    Cc: hughd@google.com
    Cc: keescook@google.com
    Cc: linux-mm@kvack.org
    Link: http://lkml.kernel.org/r/20180411152437.GC15462@8bytes.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
    e3e28812
pgtable.c 17.7 KB