From: Manish Katiyar Subject: Re: [PATCH] : make sure the buffer head members are zeroed out before using them. Date: Sun, 25 Jan 2009 21:52:44 +0530 Message-ID: References: <497C903E.5080108@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: ext4 , "Theodore Ts'o" , cmm@us.ibm.com To: Eric Sandeen Return-path: Received: from ti-out-0910.google.com ([209.85.142.186]:47010 "EHLO ti-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753768AbZAYQWq (ORCPT ); Sun, 25 Jan 2009 11:22:46 -0500 Received: by ti-out-0910.google.com with SMTP id b6so3310745tic.23 for ; Sun, 25 Jan 2009 08:22:44 -0800 (PST) In-Reply-To: <497C903E.5080108@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Sun, Jan 25, 2009 at 9:45 PM, Eric Sandeen wrote: > Manish Katiyar wrote: >> On Tue, Jan 20, 2009 at 10:36 PM, Manish Katiyar wrote: >>> ext2_quota_read doesn't bzeroes tmp_bh before calling ext2_get_block() >>> where we access the b_size of it. Since it is a local variable it >>> might contain some garbage. Make sure it is filled with zero before >>> passing. >> >> Hi Ted/mingming, >> >> Any feedback on this ?? > > This looks ok to me, Manish. I'm curious, did you see this fail in real > life, and if so, what'd the failure look like? Actually no......I realised this while going through the code. I was also wondering why we haven't hit this till now. Since ext{3,4} don't have this issue, the only reason I can think of is because ext2 with quota is not very much used or somehow we are lucky. > > With the change, the tmp_bh bh_size is 0, so maxblocks down the > get_block path is also 0, but I guess that works out ok. Yes, but that is better than having a random garbage. Isn't it ? Thanks - Manish > > -Eric > >> Thanks - >> Manish >> >>> Signed-off-by : Manish Katiyar >>> --- >>> fs/ext2/super.c | 4 ++-- >>> 1 files changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/fs/ext2/super.c b/fs/ext2/super.c >>> index da8bdea..d10aa44 100644 >>> --- a/fs/ext2/super.c >>> +++ b/fs/ext2/super.c >>> @@ -1327,7 +1327,7 @@ static ssize_t ext2_quota_read(struct >>> super_block *sb, int type, char *data, >>> tocopy = sb->s_blocksize - offset < toread ? >>> sb->s_blocksize - offset : toread; >>> >>> - tmp_bh.b_state = 0; >>> + memset(&tmp_bh, 0, sizeof(struct buffer_head)); >>> err = ext2_get_block(inode, blk, &tmp_bh, 0); >>> if (err < 0) >>> return err; >>> @@ -1366,7 +1366,7 @@ static ssize_t ext2_quota_write(struct >>> super_block *sb, int type, >>> tocopy = sb->s_blocksize - offset < towrite ? >>> sb->s_blocksize - offset : towrite; >>> >>> - tmp_bh.b_state = 0; >>> + memset(&tmp_bh, 0, sizeof(struct buffer_head)); >>> err = ext2_get_block(inode, blk, &tmp_bh, 1); >>> if (err < 0) >>> goto out; >>> -- >>> 1.5.4.3 >>> >>> >>> Thanks - >>> Manish >>> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > >