linux-kernel - Re: Re: [Intel-wired-lan] [PATCH] net: ixgbe: Fix memleak in ixgbe_configure

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Date:   Sun, 3 Jan 2021 18:03:47 +0800 (GMT+08:00)
From:   dinghao.liu@....edu.cn
To:     "Paul Menzel" <pmenzel@...gen.mpg.de>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org,
        "Jakub Kicinski" <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, kjlu@....edu
Subject: Re: Re: [Intel-wired-lan] [PATCH] net: ixgbe: Fix memleak in
 ixgbe_configure_clsu32

> Dear Dinghao,
> 
> 
> Am 03.01.21 um 09:08 schrieb Dinghao Liu:
> > When ixgbe_fdir_write_perfect_filter_82599() fails,
> > input allocated by kzalloc() has not been freed,
> > which leads to memleak.
> 
> Nice find. Thank you for your patches. Out of curiosity, do you use an 
> analysis tool to find these issues?
> 

Yes, these bugs are suggested by my static analysis tool. 

> > Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> > ---
> >   drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 6 ++++--
> >   1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> > index 393d1c2cd853..e9c2d28efc81 100644
> > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> > @@ -9582,8 +9582,10 @@ static int ixgbe_configure_clsu32(struct ixgbe_adapter *adapter,
> >   	ixgbe_atr_compute_perfect_hash_82599(&input->filter, mask);
> >   	err = ixgbe_fdir_write_perfect_filter_82599(hw, &input->filter,
> >   						    input->sw_idx, queue);
> > -	if (!err)
> > -		ixgbe_update_ethtool_fdir_entry(adapter, input, input->sw_idx);
> > +	if (err)
> > +		goto err_out_w_lock;
> > +
> > +	ixgbe_update_ethtool_fdir_entry(adapter, input, input->sw_idx);
> >   	spin_unlock(&adapter->fdir_perfect_lock);
> >   
> >   	if ((uhtid != 0x800) && (adapter->jump_tables[uhtid]))
> 
> Reviewed-by: Paul Menzel <pmenzel@...gen.mpg.de>
> 
> I wonder, in the non-error case, how `input` and `jump` are freed.
> 

I'm not sure if kfree(jump) will introduce bug. jump is allocated in a for 
loop and has been passed to adapter->jump_tables. input and mask have new
definitions (kzalloc) after this loop, it's reasonable to free them on failure.
But jump is different. Maybe we should not free jump after the loop?

> Old code:
> 
> >         if (!err)
> >                 ixgbe_update_ethtool_fdir_entry(adapter, input, input->sw_idx);
> >         spin_unlock(&adapter->fdir_perfect_lock);
> > 
> >         if ((uhtid != 0x800) && (adapter->jump_tables[uhtid]))
> >                 set_bit(loc - 1, (adapter->jump_tables[uhtid])->child_loc_map);
> > 
> >         kfree(mask);
> >         return err;
> 
> Should these two lines be replaced with `goto err_out`? (Though the name 
> is confusing then, as it’s the non-error case.)
> 

This also makes me confused. It seems that the check against untied is not error
handling code, but there is a kfree(mask) after it. Freeing allocated data on
success is not reasonable. 

Regards,
Dinghao

> > err_out_w_lock:
> >         spin_unlock(&adapter->fdir_perfect_lock);
> > err_out:
> >         kfree(mask);
> > free_input:
> >         kfree(input);
> > free_jump:
> >         kfree(jump);
> >         return err;
> > }
> 
> Kind regards,
> 
> Paul