linux-kernel - Re: [PATCH] vfs: partially sanitize i

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Date: Tue, 11 Jun 2024 13:26:45 +0200
From: Mateusz Guzik <mjguzik@...il.com>
To: Dave Chinner <david@...morbit.com>
Cc: Jan Kara <jack@...e.cz>, brauner@...nel.org, viro@...iv.linux.org.uk, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] vfs: partially sanitize i_state zeroing on inode creation

On Tue, Jun 11, 2024 at 08:56:40PM +1000, Dave Chinner wrote:
> On Tue, Jun 11, 2024 at 12:23:59PM +0200, Mateusz Guzik wrote:
> > I did not patch inode_init_always because it is exported and xfs uses it
> > in 2 spots, only one of which zeroing the thing immediately after.
> > Another one is a little more involved, it probably would not be a
> > problem as the value is set altered later anyway, but I don't want to
> > mess with semantics of the func if it can be easily avoided.
> 
> Better to move the zeroing to inode_init_always(), do the basic
> save/restore mod to xfs_reinit_inode(), and let us XFS people worry
> about whether inode_init_always() is the right thing to be calling
> in their code...
> 
> All you'd need to do in xfs_reinit_inode() is this
> 
> +	unsigned long	state = inode->i_state;
> 
> 	.....
> 	error = inode_init_always(mp->m_super, inode);
> 	.....
> +	inode->i_state = state;
> 	.....
> 
> And it should behave as expected.
> 

Ok, so what would be the logistics of submitting this?

Can I submit one patch which includes the above + i_state moved to
inode_init_always?

Do I instead ship a two-part patchset, starting with the xfs change and
stating it was your idea?

Something else?

Fwiw inode_init_always consumer rundown is:
- fs/inode.c which is automagically covered
- bcachefs pre-zeroing state before even calling inode_init_always
- xfs with one spot which zeroes immediately after the call
- xfs with one spot which possibly avoids zeroing