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From: Pavel Skripkin <paskripkin@gmail.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: davem@davemloft.net, kuba@kernel.org, linux@rempel-privat.de,
	robert.foss@collabora.com, linux-usb@vger.kernel.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	syzbot+a631ec9e717fb0423053@syzkaller.appspotmail.com
Subject: Re: [PATCH v3] net: asix: fix uninit value bugs
Date: Sat, 14 Aug 2021 19:20:21 +0300	[thread overview]
Message-ID: <5bf26e79-b612-9590-0970-09a03e0ac0ea@gmail.com> (raw)
In-Reply-To: <YRfjFr9GbcoJrycc@lunn.ch>

On 8/14/21 6:36 PM, Andrew Lunn wrote:
> On Sat, Aug 14, 2021 at 04:55:05PM +0300, Pavel Skripkin wrote:
>> Syzbot reported uninit-value in asix_mdio_read(). The problem was in
>> missing error handling. asix_read_cmd() should initialize passed stack
>> variable smsr, but it can fail in some cases. Then while condidition
>> checks possibly uninit smsr variable.
>> 
>> Since smsr is uninitialized stack variable, driver can misbehave,
>> because smsr will be random in case of asix_read_cmd() failure.
>> Fix it by adding error handling and just continue the loop instead of
>> checking uninit value.
>> 
>> Also, same loop was used in 3 other functions. Fixed uninit value bug
>> in them too.
> 
> Hi Pavel
> 
> Which suggests it might make sense to refactor the code to make a
> helper? I will leave you to decide if you want to do that.
> 
> The code does looks correct now.
> 
> 	Andrew
> 

I noticed strange thing. For example: driver looped 30 times, there 
wasn't any errors with usb transfer, but Host_En bit is not set. 
Datasheet says, that if Host_En is not set, that means software access 
will be ignored. Driver code doesn't handle this situation. We only 
check if ret is -ENODEV or -ETIMEOUT.

I guess, next register access will fail, but anyway, does it make sense 
to return when Host_En bit is not set?


With regards,
Pavel Skripkin

  parent reply	other threads:[~2021-08-14 16:20 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-13 16:01 [PATCH] net: asix: fix uninit value in asix_mdio_read Pavel Skripkin
2021-08-13 22:23 ` Andrew Lunn
2021-08-13 22:29   ` Pavel Skripkin
2021-08-13 22:42   ` [PATCH v2] " Pavel Skripkin
2021-08-13 22:52     ` Jakub Kicinski
2021-08-14 13:55       ` [PATCH v3] net: asix: fix uninit value bugs Pavel Skripkin
2021-08-14 15:36         ` Andrew Lunn
2021-08-14 15:40           ` Pavel Skripkin
2021-08-14 16:20           ` Pavel Skripkin [this message]
2021-08-17 16:37           ` [PATCH v4] " Pavel Skripkin
2021-08-18 10:50             ` patchwork-bot+netdevbpf
2021-08-13 22:57     ` [PATCH v2] net: asix: fix uninit value in asix_mdio_read Andrew Lunn

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