From: Jan Kara Subject: Re: [PATCH] ext4: use strlcpy() instead of strncpy() Date: Tue, 9 Jan 2018 11:06:55 +0100 Message-ID: <20180109100655.bdbnsrvhceaimaxh@quack2.suse.cz> References: <1515488319-23779-1-git-send-email-wangxiongfeng2@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org To: Xiongfeng Wang Return-path: Received: from mx2.suse.de ([195.135.220.15]:33595 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753870AbeAIKG5 (ORCPT ); Tue, 9 Jan 2018 05:06:57 -0500 Content-Disposition: inline In-Reply-To: <1515488319-23779-1-git-send-email-wangxiongfeng2@huawei.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue 09-01-18 16:58:39, Xiongfeng Wang wrote: > From: Xiongfeng Wang > > gcc-8 reports > > fs/ext4/super.c: In function '__save_error_info.isra.6': > ./include/linux/string.h:245:9: warning: '__builtin_strncpy' specified > bound 32 equals destination size [-Wstringop-truncation] > > We need to use strlcpy() to make sure the dest string is nul-terminated. > > Signed-off-by: Xiongfeng Wang Please have a look how s_last_error_func is used. If you do that, you'll notice that we do take care to print only sizeof(s_last_error_func) characters from the string or NUL-terminate it (in e2fsprogs). So your patch just wastes one character for useless NUL-termination... Honza > --- > fs/ext4/super.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index 7c46693..051b988 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -323,11 +323,11 @@ static void __save_error_info(struct super_block *sb, const char *func, > return; > es->s_state |= cpu_to_le16(EXT4_ERROR_FS); > es->s_last_error_time = cpu_to_le32(get_seconds()); > - strncpy(es->s_last_error_func, func, sizeof(es->s_last_error_func)); > + strlcpy(es->s_last_error_func, func, sizeof(es->s_last_error_func)); > es->s_last_error_line = cpu_to_le32(line); > if (!es->s_first_error_time) { > es->s_first_error_time = es->s_last_error_time; > - strncpy(es->s_first_error_func, func, > + strlcpy(es->s_first_error_func, func, > sizeof(es->s_first_error_func)); > es->s_first_error_line = cpu_to_le32(line); > es->s_first_error_ino = es->s_last_error_ino; > -- > 1.8.3.1 > -- Jan Kara SUSE Labs, CR