[PATCH] smc91c92_cs : add a spinlock to avoid race condition

[PATCH] smc91c92_cs : add a spinlock to avoid race condition

[Pavel Andrianov]

smc_reset may be executed in parallel with timer function media_check.
To avoid data race in smc_set_xcvr a spinlock was added.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Pavel Andrianov <andrianov@ispras.ru>
---
 drivers/net/ethernet/smsc/smc91c92_cs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/smsc/smc91c92_cs.c b/drivers/net/ethernet/smsc/smc91c92_cs.c
index db3c696..69d865c 100644
--- a/drivers/net/ethernet/smsc/smc91c92_cs.c
+++ b/drivers/net/ethernet/smsc/smc91c92_cs.c
@@ -1637,6 +1637,7 @@ static void smc_reset(struct net_device *dev)
     unsigned int ioaddr = dev->base_addr;
     struct smc_private *smc = netdev_priv(dev);
     int i;
+    unsigned long flags;
 
     netdev_dbg(dev, "smc91c92 reset called.\n");
 
@@ -1647,6 +1648,7 @@ static void smc_reset(struct net_device *dev)
     outw(RCR_SOFTRESET, ioaddr + RCR);
     udelay(10);
 
+    spin_lock_irqsave(&smc->lock, flags);
     /* Clear the transmit and receive configuration registers. */
     outw(RCR_CLEAR, ioaddr + RCR);
     outw(TCR_CLEAR, ioaddr + TCR);
@@ -1699,6 +1701,7 @@ static void smc_reset(struct net_device *dev)
     SMC_SELECT_BANK(2);
     outw((IM_EPH_INT | IM_RX_OVRN_INT | IM_RCV_INT) << 8,
 	 ioaddr + INTERRUPT);
+    spin_unlock_irqrestore(&smc->lock, flags);
 }
 
 /*======================================================================
-- 
2.7.4

Re: [PATCH] smc91c92_cs : add a spinlock to avoid race condition

[David Miller]

From: Pavel Andrianov <andrianov@ispras.ru>
Date: Tue, 16 Aug 2016 16:39:06 +0300

> smc_reset may be executed in parallel with timer function media_check.
> To avoid data race in smc_set_xcvr a spinlock was added.
> 
> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Pavel Andrianov <andrianov@ispras.ru>

This is not sufficient.

You have to block basically the entire function, because both
smc_reset and media_check program the bank selection so could
corrupt eachother's register accesses.

Re: [PATCH] smc91c92_cs : add a spinlock to avoid race condition

[Vaishali Thakkar]

On Friday 19 August 2016 09:37 AM, David Miller wrote:
> From: Pavel Andrianov <andrianov@ispras.ru>
> Date: Tue, 16 Aug 2016 16:39:06 +0300
> 
>> smc_reset may be executed in parallel with timer function media_check.
>> To avoid data race in smc_set_xcvr a spinlock was added.
>>
>> Found by Linux Driver Verification project (linuxtesting.org).
>>
>> Signed-off-by: Pavel Andrianov <andrianov@ispras.ru>
> 
> This is not sufficient.
> 
> You have to block basically the entire function, because both
> smc_reset and media_check program the bank selection so could
> corrupt eachother's register accesses.

Hmm, but then there is a use of udelay as well. Would it be still
fine to acquire a spinlock on whole function?

> 

-- 
Vaishali

Re: [PATCH] smc91c92_cs : add a spinlock to avoid race condition

[David Miller]

From: Vaishali Thakkar <vaishali.thakkar@oracle.com>
Date: Fri, 19 Aug 2016 10:11:32 +0530

> 
> 
> On Friday 19 August 2016 09:37 AM, David Miller wrote:
>> From: Pavel Andrianov <andrianov@ispras.ru>
>> Date: Tue, 16 Aug 2016 16:39:06 +0300
>> 
>>> smc_reset may be executed in parallel with timer function media_check.
>>> To avoid data race in smc_set_xcvr a spinlock was added.
>>>
>>> Found by Linux Driver Verification project (linuxtesting.org).
>>>
>>> Signed-off-by: Pavel Andrianov <andrianov@ispras.ru>
>> 
>> This is not sufficient.
>> 
>> You have to block basically the entire function, because both
>> smc_reset and media_check program the bank selection so could
>> corrupt eachother's register accesses.
> 
> Hmm, but then there is a use of udelay as well. Would it be still
> fine to acquire a spinlock on whole function?

I don't know, but what I'm telling you is that you have to execute
register programming these two functions do atomically so that the
bank selection doesn't check get changed midstream.