Re: [PATCH 6/7] btrfs: Promote to unsigned long long before shifting

From: David Sterba <dsterba@suse.cz>
To: Matthew Wilcox <willy@infradead.org>
Cc: dsterba@suse.cz, linux-fsdevel@vger.kernel.org, ericvh@gmail.com,
	lucho@ionkov.net, viro@zeniv.linux.org.uk, jlayton@kernel.org,
	idryomov@gmail.com, mark@fasheh.com, jlbec@evilplan.org,
	joseph.qi@linux.alibaba.com,
	v9fs-developer@lists.sourceforge.net,
	linux-kernel@vger.kernel.org, ceph-devel@vger.kernel.org,
	ocfs2-devel@oss.oracle.com, linux-btrfs@vger.kernel.org,
	clm@fb.com, josef@toxicpanda.com, dsterba@suse.com,
	stable@vger.kernel.org
Subject: Re: [PATCH 6/7] btrfs: Promote to unsigned long long before shifting
Date: Mon, 26 Oct 2020 18:03:54 +0100	[thread overview]
Message-ID: <20201026170354.GR6756@twin.jikos.cz> (raw)
In-Reply-To: <20201026164442.GU20115@casper.infradead.org>

On Mon, Oct 26, 2020 at 04:44:42PM +0000, Matthew Wilcox wrote:
> On Mon, Oct 26, 2020 at 05:35:46PM +0100, David Sterba wrote:
> > On Sun, Oct 04, 2020 at 07:04:27PM +0100, Matthew Wilcox (Oracle) wrote:
> > > On 32-bit systems, this shift will overflow for files larger than 4GB.
> > > 
> > > Cc: stable@vger.kernel.org
> > > Fixes: 53b381b3abeb ("Btrfs: RAID5 and RAID6")
> > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> > > ---
> > >  fs/btrfs/raid56.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
> > > index 255490f42b5d..5ee0a53301bd 100644
> > > --- a/fs/btrfs/raid56.c
> > > +++ b/fs/btrfs/raid56.c
> > > @@ -1089,7 +1089,7 @@ static int rbio_add_io_page(struct btrfs_raid_bio *rbio,
> > >  	u64 disk_start;
> > >  
> > >  	stripe = &rbio->bbio->stripes[stripe_nr];
> > > -	disk_start = stripe->physical + (page_index << PAGE_SHIFT);
> > > +	disk_start = stripe->physical + ((loff_t)page_index << PAGE_SHIFT);
> > 
> > It seems that this patch is mechanical replacement. If you check the
> > callers, the page_index is passed from an int that iterates over bits
> > set in an unsigned long (bitmap). The result won't overflow.
> 
> Not mechanical, but I clearly made mistakes.  Will you pick up the
> patches which actually fix bugs?

Yes, I just replied to the first patch, that does fix an overflow.