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    f26b4e95
    mm: avoid null pointer access in vm_struct via /proc/vmallocinfo · f26b4e95
    Mitsuo Hayasaka authored
    
    commit f5252e00 upstream
    
    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 happen:
    In __vmalloc_node() 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.
    
    Patch:
    This patch adds 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>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
    f26b4e95
    History
    mm: avoid null pointer access in vm_struct via /proc/vmallocinfo
    Mitsuo Hayasaka authored
    
    commit f5252e00 upstream
    
    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 happen:
    In __vmalloc_node() 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.
    
    Patch:
    This patch adds 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>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
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