2021-12-02 09:43:10

by Heiner Kallweit

Subject: [PATCH] mfd: lpc_ich: convert name to const char*

This change reduces the memory footprint of the structs (admittedly
not much), and it allows the compiler to store names only once.
E.g. i2c-i801 uses name "Intel PCH" twice. All users assign static
strings to name, and only usage of name is in iTCO_wdt_probe() for
printing a syslog info message. So we don't really have to worry
about potential issues like use after free.

Signed-off-by: Heiner Kallweit <[email protected]>
---
drivers/mfd/lpc_ich.c | 2 +-
include/linux/mfd/lpc_ich.h | 2 +-
include/linux/platform_data/itco_wdt.h | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/mfd/lpc_ich.c b/drivers/mfd/lpc_ich.c
index f10e53187..acb33a180 100644
--- a/drivers/mfd/lpc_ich.c
+++ b/drivers/mfd/lpc_ich.c
@@ -889,7 +889,7 @@ static int lpc_ich_finalize_wdt_cell(struct pci_dev *dev)
info = &lpc_chipset_info[priv->chipset];

pdata->version = info->iTCO_version;
- strlcpy(pdata->name, info->name, sizeof(pdata->name));
+ pdata->name = info->name;

cell->platform_data = pdata;
cell->pdata_size = sizeof(*pdata);
diff --git a/include/linux/mfd/lpc_ich.h b/include/linux/mfd/lpc_ich.h
index 39967a5ec..6dec7d992 100644
--- a/include/linux/mfd/lpc_ich.h
+++ b/include/linux/mfd/lpc_ich.h
@@ -27,7 +27,7 @@ enum {
};

struct lpc_ich_info {
- char name[32];
+ const char *name;
unsigned int iTCO_version;
unsigned int gpio_version;
enum intel_spi_type spi_type;
diff --git a/include/linux/platform_data/itco_wdt.h b/include/linux/platform_data/itco_wdt.h
index 45d860cac..c6941c089 100644
--- a/include/linux/platform_data/itco_wdt.h
+++ b/include/linux/platform_data/itco_wdt.h
@@ -19,7 +19,7 @@
* @no_reboot_use_pmc: Use PMC BXT API to set and clear NO_REBOOT bit
*/
struct itco_wdt_platform_data {
- char name[32];
+ const char *name;
unsigned int version;
bool no_reboot_use_pmc;
};
--
2.34.1

2021-12-29 13:16:30

by Lee Jones

Subject: Re: [PATCH] mfd: lpc_ich: convert name to const char*

On Thu, 02 Dec 2021, Heiner Kallweit wrote:

> This change reduces the memory footprint of the structs (admittedly
> not much), and it allows the compiler to store names only once.
> E.g. i2c-i801 uses name "Intel PCH" twice. All users assign static
> strings to name, and only usage of name is in iTCO_wdt_probe() for
> printing a syslog info message. So we don't really have to worry
> about potential issues like use after free.

Something about this patch makes me uneasy.

Honestly I'd rather copy this tiny amount of data over to a known safe
location than use pointers to potentially stale data structures.

> Signed-off-by: Heiner Kallweit <[email protected]>
> ---
> drivers/mfd/lpc_ich.c | 2 +-
> include/linux/mfd/lpc_ich.h | 2 +-
> include/linux/platform_data/itco_wdt.h | 2 +-
> 3 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mfd/lpc_ich.c b/drivers/mfd/lpc_ich.c
> index f10e53187..acb33a180 100644
> --- a/drivers/mfd/lpc_ich.c
> +++ b/drivers/mfd/lpc_ich.c
> @@ -889,7 +889,7 @@ static int lpc_ich_finalize_wdt_cell(struct pci_dev *dev)
> info = &lpc_chipset_info[priv->chipset];
>
> pdata->version = info->iTCO_version;
> - strlcpy(pdata->name, info->name, sizeof(pdata->name));
> + pdata->name = info->name;
>
> cell->platform_data = pdata;
> cell->pdata_size = sizeof(*pdata);
> diff --git a/include/linux/mfd/lpc_ich.h b/include/linux/mfd/lpc_ich.h
> index 39967a5ec..6dec7d992 100644
> --- a/include/linux/mfd/lpc_ich.h
> +++ b/include/linux/mfd/lpc_ich.h
> @@ -27,7 +27,7 @@ enum {
> };
>
> struct lpc_ich_info {
> - char name[32];
> + const char *name;
> unsigned int iTCO_version;
> unsigned int gpio_version;
> enum intel_spi_type spi_type;
> diff --git a/include/linux/platform_data/itco_wdt.h b/include/linux/platform_data/itco_wdt.h
> index 45d860cac..c6941c089 100644
> --- a/include/linux/platform_data/itco_wdt.h
> +++ b/include/linux/platform_data/itco_wdt.h
> @@ -19,7 +19,7 @@
> * @no_reboot_use_pmc: Use PMC BXT API to set and clear NO_REBOOT bit
> */
> struct itco_wdt_platform_data {
> - char name[32];
> + const char *name;
> unsigned int version;
> bool no_reboot_use_pmc;
> };

--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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