linux-ext4 - Re: [RFC 6/6] ext4: Add extra check in ext4_mb_mark_bb() to prevent against possible corruption

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Date:   Fri, 4 Feb 2022 15:41:47 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        "Theodore Ts'o" <tytso@....edu>,
        Harshad Shirwadkar <harshadshirwadkar@...il.com>
Subject: Re: [RFC 6/6] ext4: Add extra check in ext4_mb_mark_bb() to prevent
 against possible corruption

On 22/02/01 12:47PM, Jan Kara wrote:
> On Mon 31-01-22 20:46:55, Ritesh Harjani wrote:
> > This patch adds an extra checks in ext4_mb_mark_bb() function
> > to make sure we mark & report error if we were to mark/clear any
> > of the critical FS metadata specific bitmaps (&bail out) to prevent
> > from any accidental corruption.
> >
> > Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com>
>
> Again please rather use ext4_inode_block_valid() here. All the callers of
> ext4_mb_mark_bb() have the information available.
>

Same reason here too, since we are already aware of the block group these blocks
belong too, does it make any sense to check against the system-zone in that
case?

-ritesh


> 								Honza
>
> > ---
> >  fs/ext4/mballoc.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> > index 5f20e355d08c..c94888534caa 100644
> > --- a/fs/ext4/mballoc.c
> > +++ b/fs/ext4/mballoc.c
> > @@ -3920,6 +3920,13 @@ void ext4_mb_mark_bb(struct super_block *sb, ext4_fsblk_t block,
> >  		len -= overflow;
> >  	}
> >
> > +	if (!ext4_group_block_valid(sb, group, block, len)) {
> > +		ext4_error(sb, "Marking blocks in system zone - "
> > +			   "Block = %llu, len = %d", block, len);
> > +		bitmap_bh = NULL;
> > +		goto out_err;
> > +	}
> > +
> >  	clen = EXT4_NUM_B2C(sbi, len);
> >
> >  	bitmap_bh = ext4_read_block_bitmap(sb, group);
> > --
> > 2.31.1
> >
> --
> Jan Kara <jack@...e.com>
> SUSE Labs, CR