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

Kees Cook
2022-03-09T17:19:10Z

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