• Mitsuo Hayasaka's avatar
    mm: avoid null pointer access in vm_struct via /proc/vmallocinfo · f5252e00
    Mitsuo Hayasaka authored
    The /proc/vmallocinfo shows information about vmalloc allocations in
    vmlist that is a linklist of vm_struct.  It, however, may access pages
    field of vm_struct where a page was not allocated.  This results in a null
    pointer access and leads to a kernel panic.
    Why this happens: In __vmalloc_node_range() called from vmalloc(), newly
    allocated vm_struct is added to vmlist at __get_vm_area_node() and then,
    some fields of vm_struct such as nr_pages and pages are set at
    __vmalloc_area_node().  In other words, it is added to vmlist before it is
    fully initialized.  At the same time, when the /proc/vmallocinfo is read,
    it accesses the pages field of vm_struct according to the nr_pages field
    at show_numa_info().  Thus, a null pointer access happens.
    The patch adds the newly allocated vm_struct to the vmlist *after* it is
    fully initialized.  So, it can avoid accessing the pages field with
    unallocated page when show_numa_info() is called.
    Signed-off-by: default avatarMitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Namhyung Kim <namhyung@gmail.com>
    Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
    Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    Cc: <stable@kernel.org>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
vmalloc.c 65.1 KB