[PATCH] hwmon: (dimmtemp) Fix bitmap handling

[PATCH] hwmon: (dimmtemp) Fix bitmap handling

[Guenter Roeck]

Building arm:allmodconfig may fail with the following error.

In function 'fortify_memcpy_chk',
    inlined from 'bitmap_copy' at include/linux/bitmap.h:261:2,
    inlined from 'bitmap_copy_clear_tail' at include/linux/bitmap.h:270:2,
    inlined from 'bitmap_from_u64' at include/linux/bitmap.h:622:2,
    inlined from 'check_populated_dimms' at
	drivers/hwmon/peci/dimmtemp.c:284:2:
include/linux/fortify-string.h:344:25: error:
	call to '__write_overflow_field' declared with attribute warning:
	detected write beyond size of field (1st parameter)

The problematic code is
	bitmap_from_u64(priv->dimm_mask, dimm_mask);

dimm_mask is declared as u64, but the bitmap in priv->dimm_mask is only
24 bit wide. On 32-bit systems, this results in writes over the end of
the bitmap.

Fix the problem by using u32 instead of u64 for dimm_mask. This is
currently sufficient, and a compile time check to ensure that the number
of dimms does not exceed the bit map size is already in place.

Fixes: 73bc1b885dae ("hwmon: peci: Add dimmtemp driver")
Cc: Iwona Winiarska <iwona.winiarska@intel.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/peci/dimmtemp.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/peci/dimmtemp.c b/drivers/hwmon/peci/dimmtemp.c
index 3c71b5546bcb..0a633bda3668 100644
--- a/drivers/hwmon/peci/dimmtemp.c
+++ b/drivers/hwmon/peci/dimmtemp.c
@@ -220,7 +220,7 @@ static int check_populated_dimms(struct peci_dimmtemp *priv)
 	int chan_rank_max = priv->gen_info->chan_rank_max;
 	int dimm_idx_max = priv->gen_info->dimm_idx_max;
 	u32 chan_rank_empty = 0;
-	u64 dimm_mask = 0;
+	u32 dimm_mask = 0;
 	int chan_rank, dimm_idx, ret;
 	u32 pcs;
 
@@ -279,9 +279,9 @@ static int check_populated_dimms(struct peci_dimmtemp *priv)
 		return -EAGAIN;
 	}
 
-	dev_dbg(priv->dev, "Scanned populated DIMMs: %#llx\n", dimm_mask);
+	dev_dbg(priv->dev, "Scanned populated DIMMs: %#x\n", dimm_mask);
 
-	bitmap_from_u64(priv->dimm_mask, dimm_mask);
+	bitmap_from_arr32(priv->dimm_mask, &dimm_mask, DIMM_NUMS_MAX);
 
 	return 0;
 }
-- 
2.35.1

Re: [PATCH] hwmon: (dimmtemp) Fix bitmap handling

[Winiarska, Iwona]

On Tue, 2022-05-17 at 13:17 -0700, Guenter Roeck wrote:
> Building arm:allmodconfig may fail with the following error.
> 
> In function 'fortify_memcpy_chk',
>     inlined from 'bitmap_copy' at include/linux/bitmap.h:261:2,
>     inlined from 'bitmap_copy_clear_tail' at include/linux/bitmap.h:270:2,
>     inlined from 'bitmap_from_u64' at include/linux/bitmap.h:622:2,
>     inlined from 'check_populated_dimms' at
>         drivers/hwmon/peci/dimmtemp.c:284:2:
> include/linux/fortify-string.h:344:25: error:
>         call to '__write_overflow_field' declared with attribute warning:
>         detected write beyond size of field (1st parameter)
> 
> The problematic code is
>         bitmap_from_u64(priv->dimm_mask, dimm_mask);
> 
> dimm_mask is declared as u64, but the bitmap in priv->dimm_mask is only
> 24 bit wide. On 32-bit systems, this results in writes over the end of
> the bitmap.
> 
> Fix the problem by using u32 instead of u64 for dimm_mask. This is
> currently sufficient, and a compile time check to ensure that the number
> of dimms does not exceed the bit map size is already in place.
> 
> Fixes: 73bc1b885dae ("hwmon: peci: Add dimmtemp driver")
> Cc: Iwona Winiarska <iwona.winiarska@intel.com>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Reviewed-by: Iwona Winiarska <iwona.winiarska@intel.com>

Thanks
-Iwona

> ---
>  drivers/hwmon/peci/dimmtemp.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>