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Date: Wed, 22 Oct 2014 19:00:51 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Kees Cook <keescook@...omium.org> Cc: LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...nel.org>, Rik van Riel <riel@...hat.com>, David Rientjes <rientjes@...gle.com>, Aaron Tomlin <atomlin@...hat.com>, Dario Faggioli <raistlin@...ux.it>, Andi Kleen <ak@...ux.intel.com>, Peter Zijlstra <peterz@...radead.org>, Jens Axboe <axboe@...com>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, Paul Wise <pabs3@...edaddy.net> Subject: Re: [PATCH] sysctl: terminate strings also on \r On Wed, 22 Oct 2014 16:43:10 -0700 Kees Cook <keescook@...omium.org> wrote: > On Wed, Oct 22, 2014 at 4:26 PM, Andrew Morton > <akpm@...ux-foundation.org> wrote: > > On Tue, 21 Oct 2014 13:21:37 -0700 Kees Cook <keescook@...omium.org> wrote: > > > >> From: Paul Wise <pabs3@...edaddy.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. 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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