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Date:   Sat, 22 Apr 2017 15:55:21 +1000
From:   Michael Ellerman <>
To:     "Naveen N. Rao" <>,
        Masami Hiramatsu <>
Cc:     Ananth N Mavinakayanahalli <>,
        Ingo Molnar <>,,
Subject: Re: [PATCH v4 3/7] kprobes: validate the symbol name provided during probe registration

"Naveen N. Rao" <> writes:

> When a kprobe is being registered, we use the symbol_name field to
> lookup the address where the probe should be placed. Since this is a
> user-provided field, let's ensure that the length of the string is
> within expected limits.

What are we actually trying to protect against here?

If you ignore powerpc for a moment, kprobe_lookup_name() is just

All kallsyms_lookup_name() does with name is strcmp() it against a
legitimate symbol name which is at most KSYM_NAME_LEN.

So I don't think any of this validation helps in that case?

In the powerpc version of kprobe_lookup_name() we do need to do some
string juggling, for which it helps to know the input is sane. But I
think we should just make that code more robust by checking the input
before we do anything with it.


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