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    Avoid potential NULL dereference in unregister_sysctl_table · f1dad166
    Pavel Emelyanov 提交于
    register_sysctl_table() can return NULL sometimes, e.g.  when kmalloc()
    returns NULL or when sysctl check fails.
    
    I've also noticed, that many (most?) code in the kernel doesn't check for
    the return value from register_sysctl_table() and later simply calls the
    unregister_sysctl_table() with potentially NULL argument.
    
    This is unlikely on a common kernel configuration, but in case we're
    dealing with modules and/or fault-injection support, there's a slight
    possibility of an OOPS.
    
    Changing all the users to check for return code from the registering does
    not look like a good solution - there are too many code doing this and
    failure in sysctl tables registration is not a good reason to abort module
    loading (in most of the cases).
    
    So I think, that we can just have this check in unregister_sysctl_table
    just to avoid accidental OOPS-es (actually, the unregister_sysctl_table()
    did exactly this, before the start_unregistering() appeared).
    Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
    Cc: "Eric W. Biederman" <ebiederm@xmission.com>
    Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    f1dad166
sysctl.c 62.4 KB