From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sandeen.net ([63.231.237.45]:33012 "EHLO sandeen.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728710AbfDVUsJ (ORCPT ); Mon, 22 Apr 2019 16:48:09 -0400 Subject: Re: [PATCH 06/10] misc: fix strncpy length complaints References: <155594788997.115924.16224143537288136652.stgit@magnolia> <155594792809.115924.2016290538799986694.stgit@magnolia> From: Eric Sandeen Message-ID: <5e7bcc5e-7f54-f64e-e76e-94f57ed64e08@sandeen.net> Date: Mon, 22 Apr 2019 15:48:03 -0500 MIME-Version: 1.0 In-Reply-To: <155594792809.115924.2016290538799986694.stgit@magnolia> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org On 4/22/19 10:45 AM, Darrick J. Wong wrote: > From: Darrick J. Wong > > Fix a number of complaints about feeding sizeof(dest) directly to > strncpy. We do this by declaring the char arrays to be one larger > than necessary and subtracting one, to ensure that we never overfill > the buffer. > > Signed-off-by: Darrick J. Wong Hm, you don't actually do what the changelog says, do you? No buffer changes size in this patch. And FWIW, neither of these was actually a real problem (fgets guarantees a null in the string) but hey, whatever makes gcc happy I guess? (I think we lose a char in the quota array, but 511 chars ought to be enough for anybody right?) Patch seems fine, though. > --- > mkfs/xfs_mkfs.c | 13 +++++++++++-- > quota/edit.c | 9 ++++++--- > 2 files changed, 17 insertions(+), 5 deletions(-) > > > diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c > index 3e2ef92d..db3ad38e 100644 > --- a/mkfs/xfs_mkfs.c > +++ b/mkfs/xfs_mkfs.c > @@ -3270,8 +3270,17 @@ finish_superblock_setup( > struct xfs_mount *mp, > struct xfs_sb *sbp) > { > - if (cfg->label) > - strncpy(sbp->sb_fname, cfg->label, sizeof(sbp->sb_fname)); > + if (cfg->label) { > + size_t label_len; > + > + /* > + * Labels are null terminated unless the string fits exactly > + * in the label field, so assume sb_fname is zeroed and then > + * do a memcpy because the destination isn't a normal C string. > + */ > + label_len = min(sizeof(sbp->sb_fname), strlen(cfg->label)); > + memcpy(sbp->sb_fname, cfg->label, label_len); > + } > > sbp->sb_dblocks = cfg->dblocks; > sbp->sb_rblocks = cfg->rtblocks; > diff --git a/quota/edit.c b/quota/edit.c > index b10a5b34..f9938b8a 100644 > --- a/quota/edit.c > +++ b/quota/edit.c > @@ -368,8 +368,7 @@ restore_file( > uint type) > { > char buffer[512]; > - char devbuffer[512]; > - char *dev = NULL; > + char dev[512]; > uint mask; > int cnt; > uint32_t id; > @@ -377,7 +376,11 @@ restore_file( > > while (fgets(buffer, sizeof(buffer), fp) != NULL) { > if (strncmp("fs = ", buffer, 5) == 0) { > - dev = strncpy(devbuffer, buffer+5, sizeof(devbuffer)); > + /* > + * Copy the device name to dev, strip off the trailing > + * newline, and move on to the next line. > + */ > + strncpy(dev, buffer + 5, sizeof(dev) - 1); > dev[strlen(dev) - 1] = '\0'; > continue; > } >