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    SubjectRe: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of attacking

    * Linus Torvalds <torvalds@linux-foundation.org> wrote:

    > On Fri, Nov 19, 2010 at 11:19 AM, Sarah Sharp
    > <sarah.a.sharp@linux.intel.com> wrote:
    > >
    > > .config and dmesg are attached.  The box is running klogd 1.5.5ubuntu3
    > > (from Jaunty).  Yes, I know that's old.  I read the bit in the commit
    > > about changing the permissions of kallsyms after boot, but if I can't
    > > boot that doesn't help.  Perhaps this can be made a configuration
    > > option?
    >
    > It's not worth a config option.
    >
    > If it actually breaks user-space, I think we should just revert it.

    Sarah,

    Does your system boot fine if we make /proc/kallsyms simply an empty file to
    unprivileged users? Something like the (untested ...) patch below.

    Ingo

    diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
    index 6f6d091..d54c993 100644
    --- a/kernel/kallsyms.c
    +++ b/kernel/kallsyms.c
    @@ -465,7 +465,7 @@ static int s_show(struct seq_file *m, void *p)
    struct kallsym_iter *iter = m->private;

    /* Some debugging symbols have no name. Ignore them. */
    - if (!iter->name[0])
    + if (!iter->name[0] || !capable(CAP_SYS_ADMIN))
    return 0;

    if (iter->module_name[0]) {
    --
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