On Wed, Oct 22, 2014 at 7:00 PM, Andrew Morton
<[email protected]> wrote:
> On Wed, 22 Oct 2014 16:43:10 -0700 Kees Cook <[email protected]> wrote:
>
>> On Wed, Oct 22, 2014 at 4:26 PM, Andrew Morton
>> <[email protected]> wrote:
>> > On Tue, 21 Oct 2014 13:21:37 -0700 Kees Cook <[email protected]> wrote:
>> >
>> >> From: Paul Wise <[email protected]>
>> >>
>> >> This partially mitigates a common strategy used by attackers for hiding
>> >> the full contents of strings in procfs from naive sysadmins who use cat,
>> >> more or sysctl to inspect the contents of strings in procfs.
>> >>
>> >> ...
>> >>
>> >> --- a/kernel/sysctl.c
>> >> +++ b/kernel/sysctl.c
>> >> @@ -1739,7 +1739,7 @@ static int _proc_do_string(char *data, int maxlen,
>> >> int write,
>> >> while ((p - buffer) < *lenp && len < maxlen - 1) {
>> >> if (get_user(c, p++))
>> >> return -EFAULT;
>> >> - if (c == 0 || c == '\n')
>> >> + if (c == 0 || c == '\n' || c == '\r')
>> >> break;
>> >> data[len++] = c;
>> >> }
>> >
>> > There are no valid uses of \r in a procfs write?
>>
>> I struggle to imagine one; everything I found that uses proc_dostring
>> seems to be names, paths, and commands.
>>
>
> You're insufficiently pessimistic.
Haha, I haven't had that accusation made about me before; I'll keep
this quote around! :)
> I wonder if the chances of damage would be lower if we were to continue
> to accept the \r, but turn it into something else ("\r"?) when it is
> read.
I think that would complicate things more than help them. If there's a
legit use of \r, I'll let Paul Wise debate how to proceed. :)
-Kees
--
Kees Cook
Chrome OS Security
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