Re: [PATCH v2 2/2] dmaengine: pxa: Enable compile test

[Krzysztof Kozlowski <krzk@kernel.org>]

On 21/03/2025 15:57, Dan Carpenter wrote:
> [ Ancient email got eaten by msmtp. Resending.  -dan ]
> 
> Hi Krzysztof,
> 
> kernel test robot noticed the following build warnings:
> 
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Krzysztof-Kozlowski/dmaengine-pxa-Enable-compile-test/20250115-031547
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/vkoul/dmaengine.git next
> patch link:    https://lore.kernel.org/r/20250114191316.857154-1-krzysztof.kozlowski%40linaro.org
> patch subject: [PATCH v2 2/2] dmaengine: pxa: Enable compile test
> config: parisc-randconfig-r072-20250124 (https://download.01.org/0day-ci/archive/20250125/202501252153.wCMpgWlF-lkp@intel.com/config)
> compiler: hppa-linux-gcc (GCC) 14.2.0
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> | Closes: https://lore.kernel.org/r/202501252153.wCMpgWlF-lkp@intel.com/
> 
> New smatch warnings:
> drivers/dma/pxa_dma.c:595 clear_chan_irq() warn: variable dereferenced before check 'phy->vchan' (see line 593)
> 
> vim +595 drivers/dma/pxa_dma.c
> 
> a57e16cf03339c Robert Jarzmik 2015-05-25  584  static unsigned int clear_chan_irq(struct pxad_phy *phy)
> a57e16cf03339c Robert Jarzmik 2015-05-25  585  {
> a57e16cf03339c Robert Jarzmik 2015-05-25  586  	u32 dcsr;
> a57e16cf03339c Robert Jarzmik 2015-05-25  587  	u32 dint = readl(phy->base + DINT);
> a57e16cf03339c Robert Jarzmik 2015-05-25  588  
> a57e16cf03339c Robert Jarzmik 2015-05-25  589  	if (!(dint & BIT(phy->idx)))
> a57e16cf03339c Robert Jarzmik 2015-05-25  590  		return PXA_DCSR_RUN;
> a57e16cf03339c Robert Jarzmik 2015-05-25  591  
> a57e16cf03339c Robert Jarzmik 2015-05-25  592  	/* clear irq */
> a57e16cf03339c Robert Jarzmik 2015-05-25 @593  	dcsr = phy_readl_relaxed(phy, DCSR);
>                                                                          ^^^
> if phy->vchan is NULL this will crash


Correct, but my commit only enabled compile testing thus allowed this to
be checked on some popular platforms. Issue was already there.

The code is called pxad_chan_handler(), which already has BUG_ON() on
this, so I expect that condition is not possible.

It would be nice to rewrite the code, but I am afraid it is way too old
platform and no one cares enough.

Best regards,
Krzysztof