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From: Pavel Herrmann <morpheus.ibis@gmail.com>
To: linux-arm-kernel@lists.infradead.org
Subject: Re: [lm-sensors] [PATCH v3] MAX1111: Fix Race condition causing
Date: Tue, 12 Jul 2011 08:04:55 +0000	[thread overview]
Message-ID: <1628512.b7CSRB10BJ@bloomfield> (raw)
In-Reply-To: <20110712093606.5db834cb@endymion.delvare>

On Tuesday 12 of July 2011 09:36:06 Jean Delvare wrote:
> On Mon, 11 Jul 2011 23:50:38 +0200, Pavel Herrmann wrote:
> > spi_sync call uses its spi_message parameter to keep completion
> > information, using a drvdata structure is not thread-safe, potentially
> > causing one thread having pointers to memory on or above other threads
> > stack. use mutex to prevent multiple access
> 
> Honestly, I have no idea what "causing one thread having pointers to
> memory on or above other threads stack" means (nor why this would be
> bad.)

the long-winded story is that thread A writes a pointer onto its stack into 
the drvdata as part of spi_sync call, then thread B comes in and puts a 
pointer onto its stack into the drvdata, at the end of spi_sync thread A uses 
this pointer (assuming it is unchanged), which is pointing either onto valid 
stack of thread B or somewhere above it (if thread B already returned)

> Patch applied nevertheless, as it fixes an actual bug which should be
> fixed ASAP. Thanks for your contribution.

thanks

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WARNING: multiple messages have this Message-ID (diff)
From: morpheus.ibis@gmail.com (Pavel Herrmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3] MAX1111: Fix Race condition causing NULL pointer exception
Date: Tue, 12 Jul 2011 10:04:55 +0200	[thread overview]
Message-ID: <1628512.b7CSRB10BJ@bloomfield> (raw)
In-Reply-To: <20110712093606.5db834cb@endymion.delvare>

On Tuesday 12 of July 2011 09:36:06 Jean Delvare wrote:
> On Mon, 11 Jul 2011 23:50:38 +0200, Pavel Herrmann wrote:
> > spi_sync call uses its spi_message parameter to keep completion
> > information, using a drvdata structure is not thread-safe, potentially
> > causing one thread having pointers to memory on or above other threads
> > stack. use mutex to prevent multiple access
> 
> Honestly, I have no idea what "causing one thread having pointers to
> memory on or above other threads stack" means (nor why this would be
> bad.)

the long-winded story is that thread A writes a pointer onto its stack into 
the drvdata as part of spi_sync call, then thread B comes in and puts a 
pointer onto its stack into the drvdata, at the end of spi_sync thread A uses 
this pointer (assuming it is unchanged), which is pointing either onto valid 
stack of thread B or somewhere above it (if thread B already returned)

> Patch applied nevertheless, as it fixes an actual bug which should be
> fixed ASAP. Thanks for your contribution.

thanks

  reply	other threads:[~2011-07-12  8:04 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-07-11 21:50 [lm-sensors] [PATCH v3] MAX1111: Fix Race condition causing NULL Pavel Herrmann
2011-07-11 21:50 ` [PATCH v3] MAX1111: Fix Race condition causing NULL pointer exception Pavel Herrmann
2011-07-12  7:36 ` [lm-sensors] [PATCH v3] MAX1111: Fix Race condition causing Jean Delvare
2011-07-12  7:36   ` [PATCH v3] MAX1111: Fix Race condition causing NULL pointer exception Jean Delvare
2011-07-12  8:04   ` Pavel Herrmann [this message]
2011-07-12  8:04     ` Pavel Herrmann
2011-07-12  8:22     ` [lm-sensors] [PATCH v3] MAX1111: Fix Race condition Mark Brown
2011-07-12  8:22       ` [lm-sensors] [PATCH v3] MAX1111: Fix Race condition causing NULL pointer exception Mark Brown
2011-07-12  8:40     ` [lm-sensors] [PATCH v3] MAX1111: Fix Race condition causing Jean Delvare
2011-07-12  8:40       ` [PATCH v3] MAX1111: Fix Race condition causing NULL pointer exception Jean Delvare

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