linux-kernel - Re: [PATCH] tpm/tpm_i2c_stm_st33: Check return code of get

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Message-ID: <20131030000618.GA5241@kroah.com>
Date:	Tue, 29 Oct 2013 17:06:18 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Peter Huewe <peterhuewe@....de>
Cc:	Ashley Lai <ashley@...leylai.com>, Rajiv Andrade <mail@...jiv.net>,
	Marcel Selhorst <tpmdd@...horst.net>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] tpm/tpm_i2c_stm_st33: Check return code of
 get_burstcount (fix CID: 986658)

On Wed, Oct 30, 2013 at 12:54:20AM +0100, Peter Huewe wrote:
> Coverity complains about
> "Improper use of negative value
> The negative value may be unexpected by later operations, causing
> incorrect computations.
> In tpm_stm_i2c_send: Negative value can be returned from function is not
> being checked before being used improperly (CWE-394)"
> 
> The 'get_burstcount' function can in some circumstances 'return -EBUSY' which
> in tpm_stm_i2c_send is stored in an 'u32 burstcnt'
> thus converting the signed value into an unsigned value, resulting
> in 'burstcnt' being huge.
> Changing the type to u32 only does not solve the problem as the signed
> value is converted to an unsigned in I2C_WRITE_DATA, resulting in the
> same effect.
> 
> Thus
> -> Change type of burstcnt to u32 (the return type of get_burstcount)
> -> Add a check for the return value of 'get_burstcount' and propagate a
> potential error.
> 
> This makes also sense in the 'I2C_READ_DATA' case, where the there is no
> signed/unsigned conversion.
> 
> CID: 986658

What is this field for?

thanks,

greg k-h
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