[kernel-hardening] Re: [PATCH 1/3] kallsyms: don't leak address when symbol not found

Tobin C. Harding
2017-12-18T22:41:29Z

On Mon, Dec 18, 2017, at 20:55, Felix Fietkau wrote:
> On 2017-12-18 00:53, Tobin C. Harding wrote:
> > Currently if kallsyms_lookup() fails to find the symbol then the address
> > is printed. This potentially leaks sensitive information. Instead of
> > printing the address we can return an error, giving the calling code the
> > option to print the address or print some sanitized message.
> >
> > Return error instead of printing address to argument buffer. Leave
> > buffer in a sane state.
> >
> > Signed-off-by: Tobin C. Harding <me@tobin.cc>
> I think there should be a way to keep the old behavior for debugging.

That was the intended use of

EXPORT_SYMBOL(string_is_no_symbol);

in patch 2 of this series. Then if debugging behaviour is adversely
effected one could use string_is_no_symbol() on a case by case basis to
add back in the original behaviour.

Current suggestion on list is to remove this function. Do you have a use
case in mind where debugging will break? We could add a fix to this
series if so. Otherwise next version will likely drop
string_is_no_symbol()

thanks,
Tobin.