Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934866Ab3DHDw5 (ORCPT ); Sun, 7 Apr 2013 23:52:57 -0400 Received: from mail-ee0-f54.google.com ([74.125.83.54]:40662 "EHLO mail-ee0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934777Ab3DHDw4 (ORCPT ); Sun, 7 Apr 2013 23:52:56 -0400 MIME-Version: 1.0 In-Reply-To: <5162390C.5060804@asianux.com> References: <5162390C.5060804@asianux.com> From: KOSAKI Motohiro Date: Sun, 7 Apr 2013 23:52:34 -0400 Message-ID: Subject: Re: [PATCH] kernel: tsacct: strncpy, always be sure of NUL terminated. To: Chen Gang Cc: "Eric W. Biederman" , Frederic Weisbecker , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1406 Lines: 34 On Sun, Apr 7, 2013 at 11:27 PM, Chen Gang wrote: > > for NUL terminated string, always set '\0' at the end. > > Signed-off-by: Chen Gang > --- > kernel/tsacct.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/kernel/tsacct.c b/kernel/tsacct.c > index a1dd9a1..01bcc4e 100644 > --- a/kernel/tsacct.c > +++ b/kernel/tsacct.c > @@ -78,7 +78,8 @@ void bacct_add_tsk(struct user_namespace *user_ns, > stats->ac_minflt = tsk->min_flt; > stats->ac_majflt = tsk->maj_flt; > > - strncpy(stats->ac_comm, tsk->comm, sizeof(stats->ac_comm)); > + strncpy(stats->ac_comm, tsk->comm, sizeof(stats->ac_comm) - 1); > + stats->ac_comm[sizeof(stats->ac_comm) - 1] = '\0'; sizeof(tsk->comm) is 16 and sizeof(stats->ac_comm) is 32. then this statement is strange. and set_task_comm ensure tsk->comm is nul-terminated. so your code never change the behavior, right? And, If buggy driver change tsk->comm not to use set_task_comm and tsk->comm is not nul-terminated, strncpy() still touch unrelated memory and ac_comm may expose kernel internal info. that's bad. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/