linux-kernel - Re: [PATCH v2] staging: vchiq

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Message-ID: <20180312111421.zckzwhspwgcq2vpi@mwanda>
Date:   Mon, 12 Mar 2018 14:14:22 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Stefan Wahren <stefan.wahren@...e.com>
Cc:     Eric Anholt <eric@...olt.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Tobin C. Harding" <me@...in.cc>, linux-kernel@...r.kernel.org,
        Tycho Andersen <tycho@...ho.ws>,
        driverdev-devel@...uxdriverproject.org,
        Kees Cook <keescook@...omium.org>,
        kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v2] staging: vchiq_arm: Clear VLA warning

On Mon, Mar 12, 2018 at 06:58:04AM +0100, Stefan Wahren wrote:
> Hi Tobin,
> 
> > "Tobin C. Harding" <me@...in.cc> hat am 12. März 2018 um 06:46 geschrieben:
> > 
> > 
> > On Mon, Mar 12, 2018 at 12:37:53PM +1100, Tobin C. Harding wrote:
> > > The kernel would like to have all stack VLA usage removed[1].  The array
> > > here is fixed (declared with a const variable) but it appears like a VLA
> > > to the compiler.  Also, currently we are putting 768 bytes on the
> > > stack.  This function is only called on the error path so performance is
> > > not critical, let's just allocate the memory instead of using the
> > > stack.  This saves stack space and removes the VLA build warning.
> > > 
> > > kmalloc a buffer for dumping state instead of using the stack.
> > > 
> > > [1]: https://lkml.org/lkml/2018/3/7/621
> > > 
> > > Signed-off-by: Tobin C. Harding <me@...in.cc>
> > > ---
> > 
> > Drop this please, leaks memory.
> 
> except from the leak, did you test this patch on a RPi?
> 

Hm...  Yeah.  It looks like we're holding a mutex when we call
vchiq_check_service() from vchiq_queue_message().

regards,
dan carpenter