linux-ext4 - Re: [PATCH] : make sure the buffer head members are zeroed out before using them.

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Message-ID: <ea11fea30901260433i6d06ea49v8524c46ad373733f@mail.gmail.com>
Date:	Mon, 26 Jan 2009 18:03:19 +0530
From:	Manish Katiyar <mkatiyar@...il.com>
To:	Jan Kara <jack@...e.cz>
Cc:	ext4 <linux-ext4@...r.kernel.org>, "Theodore Ts'o" <tytso@....edu>,
	cmm@...ibm.com
Subject: Re: [PATCH] : make sure the buffer head members are zeroed out before 
	using them.

On Mon, Jan 26, 2009 at 5:59 PM, Jan Kara <jack@...e.cz> wrote:
>> On Tue, Jan 20, 2009 at 10:36 PM, Manish Katiyar <mkatiyar@...il.com> 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 ??
>  Ops, sorry. I wanted to reply but first I wanted to research more
> whether we can set b_size to 0 and then forgot about it. Looking into
> other code (e.g. in fs/mpage.c or fs/buffer.c) I think it would be
> better to set b_size to sb->s_blocksize and be done with that. Mapping
> code does not need anything else set to a deterministic value so using
> memset is a bit overkill.

Thanks Jan for your comments. Yes memset is an overkill. I did it just
because other users of ext2_get_block were doing the same way. Will
rework the patch with setting b_size as blocksize and send again.

Thanks -
Manish

>
>                                                                Honza
>
>> > Signed-off-by : Manish Katiyar <mkatiyar@...il.com>
>> > ---
>> >  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
>> >
>> --
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> --
> Jan Kara <jack@...e.cz>
> SuSE CR Labs
>
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