linux-kernel - Re: linux-next: build failure after merge of the kspp tree

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Date:   Wed, 9 Mar 2022 09:18:26 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Mark Gross <markgross@...nel.org>,
        Mark Pearson <markpearson@...ovo.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: build failure after merge of the kspp tree

On Wed, Mar 09, 2022 at 05:58:56PM +0100, Hans de Goede wrote:
> Hi,
> 
> On 3/9/22 17:52, Kees Cook wrote:
> > On Wed, Mar 09, 2022 at 09:10:29PM +1100, Stephen Rothwell wrote:
> >> Hi all,
> >>
> >> After merging the kspp tree, today's linux-next build (x86_64
> >> allmodconfig) failed like this:
> >>
> >> In file included from include/linux/bitops.h:33,
> >>                  from include/linux/kernel.h:22,
> >>                  from drivers/platform/x86/thinkpad_acpi.c:37:
> >> drivers/platform/x86/thinkpad_acpi.c: In function 'tpacpi_dytc_profile_init':
> >> arch/x86/include/asm/bitops.h:207:22: error: array subscript 'long unsigned int[0]' is partly outside array bounds of 'int[1]' [-Werror=array-bounds]
> >>   207 |                 (addr[nr >> _BITOPS_LONG_SHIFT])) != 0;
> >>       |                 ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
> >> drivers/platform/x86/thinkpad_acpi.c:10385:18: note: while referencing 'output'
> >> 10385 |         int err, output;
> >>       |                  ^~~~~~
> >>
> >> Actually the test_bit() in line 10409.
> >>
> >> Caused by commit
> >>
> >>   e1c21608e3cf ("platform/x86: thinkpad_acpi: Add PSC mode support")
> >>
> >> from the drivers-x86 tree interacting with the enablement of
> >> -Werror=array-bounds.
> >>
> >> I have reverted that commit for today.
> 
> Thank you.
> 
> > Looking at https://lore.kernel.org/all/20220225182505.7234-1-markpearson@lenovo.com/
> > 
> > The problem is with the cast of "int output" to "unsigned long". Past
> > fixes have either made the variable unsigned long, or adding a new
> > variable and removal of casts. e.g. this pseudo-patch:
> > 
> > +	unsigned long bits;
> > 
> > 	...
> > +	bits = output;
> > -	if (test_bit(DYTC_FC_MMC, (void *)&output)) { /* MMC MODE */
> > +	if (test_bit(DYTC_FC_MMC, &bits)) { /* MMC MODE */
> > 
> > ...
> > 
> > -	} else if (test_bit(DYTC_FC_PSC, (void *)&output)) { /*PSC MODE */
> > +	} else if (test_bit(DYTC_FC_PSC, &bits)) { /*PSC MODE */
> 
> Right I was just preparing a patch for this, I've gone with:
> 
> diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
> index 7016c7fc3440..c476a78599d6 100644
> --- a/drivers/platform/x86/thinkpad_acpi.c
> +++ b/drivers/platform/x86/thinkpad_acpi.c
> @@ -10399,7 +10399,7 @@ static int tpacpi_dytc_profile_init(struct ibm_init_struct *iibm)
>  	if (err)
>  		return err;
>  
> -	if (test_bit(DYTC_FC_MMC, (void *)&output)) { /* MMC MODE */
> +	if (output & BIT(DYTC_FC_MMC)) { /* MMC MODE */
>  		dytc_profile_available = DYTC_FUNCMODE_MMC;
>  
>  		/*
> @@ -10412,7 +10412,7 @@ static int tpacpi_dytc_profile_init(struct ibm_init_struct *iibm)
>  			if (!err && ((output & DYTC_ERR_MASK) == DYTC_ERR_SUCCESS))
>  				dytc_mmc_get_available = true;
>  		}
> -	} else if (test_bit(DYTC_FC_PSC, (void *)&output)) { /*PSC MODE */
> +	} else if (output & BIT(DYTC_FC_PSC)) { /* PSC MODE */
>  		dytc_profile_available = DYTC_FUNCMODE_PSC;
>  	} else {
>  		dbg_printk(TPACPI_DBG_INIT, "No DYTC support available\n");
> 
> I'll push this to the drivers-x86 tree for-next branch.

Ah yeah. Heh, that's much simpler. :)

-- 
Kees Cook