netdev - Re: [PATCH v2] i40e: fix return of uninitialized aq_ret in i40e_set_vsi

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Date:   Thu, 13 Aug 2020 13:46:27 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Stefan Assmann <sassmann@...nic.de>
Cc:     intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        davem@...emloft.net, jeffrey.t.kirsher@...el.com,
        lihong.yang@...el.com
Subject: Re: [PATCH v2] i40e: fix return of uninitialized aq_ret in
 i40e_set_vsi_promisc

On Thu, 13 Aug 2020 13:26:38 +0200 Stefan Assmann wrote:
> drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c: In function ‘i40e_set_vsi_promisc’:
> drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c:1176:14: error: ‘aq_ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>   i40e_status aq_ret;
> 
> In case the code inside the if statement and the for loop does not get
> executed aq_ret will be uninitialized when the variable gets returned at
> the end of the function.
> 
> Avoid this by changing num_vlans from int to u16, so aq_ret always gets
> set. Making this change in additional places as num_vlans should never
> be negative.
> 
> Fixes: 37d318d7805f ("i40e: Remove scheduling while atomic possibility")
> Signed-off-by: Stefan Assmann <sassmann@...nic.de>

Acked-by: Jakub Kicinski <kuba@...nel.org>

Good enough - in general unless you're trying to save space using types
other than unsigned int is not really worth it, and can slow the code
down - since 2B arithmetic is actually slowest on modern CPUs. But it's
not a fast path, so doesn't matter much.