netdev - Re: Bluetooth fixes for 2.6.20-rc4

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Message-Id: <1168220681.12025.26.camel@violet>
Date:	Mon, 08 Jan 2007 02:44:41 +0100
From:	Marcel Holtmann <marcel@...tmann.org>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: Bluetooth fixes for 2.6.20-rc4

Hi Dave,

> > > > Commit: 2b2e64be763c5e64d4ae4a061825b18decf1edf7 
> > > > Author: Marcel Holtmann <marcel@...tmann.org> Mon, 08 Jan 2007 01:00:33 +0100 
> > > > 
> > > >     [Bluetooth] Fix uninitialized return value for RFCOMM sendmsg()
> > > >     
> > > >     When calling send() with a zero length parameter on a RFCOMM socket
> > > >     it returns a positive value. In this rare case the variable err is
> > > >     used uninitialized and unfortunately its value is returned.
> > > >     
> > > >     Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
> > > 
> > > You can't fix this bug like that.
> > > 
> > > If sendmsg() sends any bytes, it should return the number of
> > > bytes sent even if an error occurs mid-stream.
> > > 
> > > With this change, you'll now return the error instead of
> > > the number of bytes sent.  That's what the new "sent = err"
> > > assignment does.
> > > 
> > > You have to do sendmsg() with those semantics, or else you lose
> > > information in that the user can never know how many bytes were
> > > actually sent successfully.  Losing the error after successfully sent
> > > bytes is OK, if the error persists the user will get it when it
> > > recalls sendmsg() to push the rest of the remaining bytes out.
> > > 
> > > The original code tried to do it right.
> > > 
> > > If the bug is that 'err' is uninitialized, why try to fix this
> > > by being fancy, just initialize it :-)
> > 
> > We have "int sent = 0" and exactly that is returned if "len == 0".
> 
> Marcel, please reread my email, then you can hit reply again ok :)
> 
> You broke the case where len != 0, you're going to return an error
> code when "sent != 0" and that's a bug, sendmsg() must return the
> number of bytes sent if non-zero even if an error occurs.

it is way too late and you are absolutely right. However since the
current code doesn't produce a compiler warning of an uninitialized
variable, I prefer to not go with a "int err = 0" to make this work.

I rebuild the tree with the correct fix in it and it is now ready to be
pulled.

Regards

Marcel


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