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

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Date:	Mon, 26 Jan 2009 18:18:19 +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 6:03 PM, Manish Katiyar <mkatiyar@...il.com> wrote:
> 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.

Here is the updated patch. compile tested.

Signed-off-by : Manish Katiyar <mkatiyar@...il.com>
---
 fs/ext2/super.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index da8bdea..2a1c0c6 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -1328,6 +1328,7 @@ static ssize_t ext2_quota_read(struct
super_block *sb, int type, char *data,
 				sb->s_blocksize - offset : toread;

 		tmp_bh.b_state = 0;
+		tmp_bh.b_size = sb->s_blocksize;
 		err = ext2_get_block(inode, blk, &tmp_bh, 0);
 		if (err < 0)
 			return err;
@@ -1367,6 +1368,7 @@ static ssize_t ext2_quota_write(struct
super_block *sb, int type,
 				sb->s_blocksize - offset : towrite;

 		tmp_bh.b_state = 0;
+		tmp_bh.b_size = sb->s_blocksize;
 		err = ext2_get_block(inode, blk, &tmp_bh, 1);
 		if (err < 0)
 			goto out;
-- 
1.5.4.3



Thanks -
Manish


>
> 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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