Messages in this thread | | | Date | Thu, 23 Oct 2014 09:39:09 -0700 | Subject | Re: [PATCH] sysctl: terminate strings also on \r | From | Kees Cook <> |
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On Wed, Oct 22, 2014 at 7:00 PM, Andrew Morton <akpm@linux-foundation.org> wrote: > On Wed, 22 Oct 2014 16:43:10 -0700 Kees Cook <keescook@chromium.org> wrote: > >> On Wed, Oct 22, 2014 at 4:26 PM, Andrew Morton >> <akpm@linux-foundation.org> wrote: >> > On Tue, 21 Oct 2014 13:21:37 -0700 Kees Cook <keescook@chromium.org> wrote: >> > >> >> From: Paul Wise <pabs3@bonedaddy.net> >> >> >> >> 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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