• Hong H. Pham's avatar
    powerpc: Fix PTE page address mismatch in pgtable ctor/dtor · cf77ee54
    Hong H. Pham authored
    In pte_alloc_one(), pgtable_page_ctor() is passed an address that has
    not been converted by page_address() to the newly allocated PTE page.
    
    When the PTE is freed, __pte_free_tlb() calls pgtable_page_dtor()
    with an address to the PTE page that has been converted by page_address().
    The mismatch in the PTE's page address causes pgtable_page_dtor() to access
    invalid memory, so resources for that PTE (such as the page lock) is not
    properly cleaned up.
    
    On PPC32, only SMP kernels are affected.
    
    On PPC64, only SMP kernels with 4K page size are affected.
    
    This bug was introduced by commit d614bb04
    "powerpc: Move the pte free routines from common header".
    
    On a preempt-rt kernel, a spinlock is dynamically allocated for each
    PTE in pgtable_page_ctor().  When the PTE is freed, calling
    pgtable_page_dtor() with a mismatched page address causes a memory leak,
    as the pointer to the PTE's spinlock is bogus.
    
    On mainline, there isn't any immediately obvious symptoms, but the
    problem still exists here.
    
    Fixes: d614bb04 "powerpc: Move the pte free routes from common header"
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: linux-stable <stable@vger.kernel.org> # v3.10+
    Signed-off-by: default avatarHong H. Pham <hong.pham@windriver.com>
    Reviewed-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    cf77ee54
pgalloc-32.h 2.6 KB