[PATCH] dell-smbios: fix string overflow

[PATCH] dell-smbios: fix string overflow

[Arnd Bergmann]

The new sysfs code overwrites two fixed-length character arrays
that are each one byte shorter than they need to be, to hold
the trailing \0:

drivers/platform/x86/dell-smbios.c: In function 'build_tokens_sysfs':
drivers/platform/x86/dell-smbios.c:494:42: error: 'sprintf' writing a terminating nul past the end of the destination [-Werror=format-overflow=]
   sprintf(buffer_location, "%04x_location",
drivers/platform/x86/dell-smbios.c:494:3: note: 'sprintf' output 14 bytes into a destination of size 13
drivers/platform/x86/dell-smbios.c:506:36: error: 'sprintf' writing a terminating nul past the end of the destination [-Werror=format-overflow=]
   sprintf(buffer_value, "%04x_value",
drivers/platform/x86/dell-smbios.c:506:3: note: 'sprintf' output 11 bytes into a destination of size 10

This changes it to just use kasprintf(), which always gets it right.

Fixes: 33b9ca1e53b4 ("platform/x86: dell-smbios: Add a sysfs interface for SMBIOS tokens")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/platform/x86/dell-smbios.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/platform/x86/dell-smbios.c b/drivers/platform/x86/dell-smbios.c
index d99edd803c19..6a60db515bda 100644
--- a/drivers/platform/x86/dell-smbios.c
+++ b/drivers/platform/x86/dell-smbios.c
@@ -463,8 +463,6 @@ static struct platform_driver platform_driver = {
 
 static int build_tokens_sysfs(struct platform_device *dev)
 {
-	char buffer_location[13];
-	char buffer_value[10];
 	char *location_name;
 	char *value_name;
 	size_t size;
@@ -491,9 +489,8 @@ static int build_tokens_sysfs(struct platform_device *dev)
 		if (da_tokens[i].tokenID == 0)
 			continue;
 		/* add location */
-		sprintf(buffer_location, "%04x_location",
-			da_tokens[i].tokenID);
-		location_name = kstrdup(buffer_location, GFP_KERNEL);
+		location_name = kasprintf(GFP_KERNEL, "%04x_location",
+					  da_tokens[i].tokenID);
 		if (location_name == NULL)
 			goto out_unwind_strings;
 		sysfs_attr_init(&token_location_attrs[i].attr);
@@ -503,9 +500,8 @@ static int build_tokens_sysfs(struct platform_device *dev)
 		token_attrs[j++] = &token_location_attrs[i].attr;
 
 		/* add value */
-		sprintf(buffer_value, "%04x_value",
-			da_tokens[i].tokenID);
-		value_name = kstrdup(buffer_value, GFP_KERNEL);
+		value_name = kasprintf(GFP_KERNEL, "%04x_value",
+				       da_tokens[i].tokenID);
 		if (value_name == NULL)
 			goto loop_fail_create_value;
 		sysfs_attr_init(&token_value_attrs[i].attr);
-- 
2.9.0

Re: [PATCH] dell-smbios: fix string overflow

[sathyanarayanan kuppuswamy]

Hi,

I recommend using "platform/x86: dell-smbios:" in commit header.

On 11/08/2017 04:08 AM, Arnd Bergmann wrote:
> The new sysfs code overwrites two fixed-length character arrays
> that are each one byte shorter than they need to be, to hold
> the trailing \0:
>
> drivers/platform/x86/dell-smbios.c: In function 'build_tokens_sysfs':
> drivers/platform/x86/dell-smbios.c:494:42: error: 'sprintf' writing a terminating nul past the end of the destination [-Werror=format-overflow=]
>     sprintf(buffer_location, "%04x_location",
> drivers/platform/x86/dell-smbios.c:494:3: note: 'sprintf' output 14 bytes into a destination of size 13
> drivers/platform/x86/dell-smbios.c:506:36: error: 'sprintf' writing a terminating nul past the end of the destination [-Werror=format-overflow=]
>     sprintf(buffer_value, "%04x_value",
> drivers/platform/x86/dell-smbios.c:506:3: note: 'sprintf' output 11 bytes into a destination of size 10
Don't need to include the error log in commit message. Just explaining 
the issue is good enough.
>
> This changes it to just use kasprintf(), which always gets it right.
>
> Fixes: 33b9ca1e53b4 ("platform/x86: dell-smbios: Add a sysfs interface for SMBIOS tokens")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>   drivers/platform/x86/dell-smbios.c | 12 ++++--------
>   1 file changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/platform/x86/dell-smbios.c b/drivers/platform/x86/dell-smbios.c
> index d99edd803c19..6a60db515bda 100644
> --- a/drivers/platform/x86/dell-smbios.c
> +++ b/drivers/platform/x86/dell-smbios.c
> @@ -463,8 +463,6 @@ static struct platform_driver platform_driver = {
>   
>   static int build_tokens_sysfs(struct platform_device *dev)
>   {
> -	char buffer_location[13];
> -	char buffer_value[10];
>   	char *location_name;
>   	char *value_name;
>   	size_t size;
> @@ -491,9 +489,8 @@ static int build_tokens_sysfs(struct platform_device *dev)
>   		if (da_tokens[i].tokenID == 0)
>   			continue;
>   		/* add location */
> -		sprintf(buffer_location, "%04x_location",
> -			da_tokens[i].tokenID);
> -		location_name = kstrdup(buffer_location, GFP_KERNEL);
> +		location_name = kasprintf(GFP_KERNEL, "%04x_location",
> +					  da_tokens[i].tokenID);
>   		if (location_name == NULL)
>   			goto out_unwind_strings;
>   		sysfs_attr_init(&token_location_attrs[i].attr);
> @@ -503,9 +500,8 @@ static int build_tokens_sysfs(struct platform_device *dev)
>   		token_attrs[j++] = &token_location_attrs[i].attr;
>   
>   		/* add value */
> -		sprintf(buffer_value, "%04x_value",
> -			da_tokens[i].tokenID);
> -		value_name = kstrdup(buffer_value, GFP_KERNEL);
> +		value_name = kasprintf(GFP_KERNEL, "%04x_value",
> +				       da_tokens[i].tokenID);
>   		if (value_name == NULL)
>   			goto loop_fail_create_value;
>   		sysfs_attr_init(&token_value_attrs[i].attr);

-- 
Sathyanarayanan Kuppuswamy
Linux kernel developer

RE: [PATCH] dell-smbios: fix string overflow

[Mario.Limonciello]

> -----Original Message-----
> From: sathyanarayanan kuppuswamy
> [mailto:sathyanarayanan.kuppuswamy@linux.intel.com]
> Sent: Wednesday, November 8, 2017 12:23 PM
> To: Arnd Bergmann <arnd@arndb.de>; Pali Rohár <pali.rohar@gmail.com>;
> Limonciello, Mario <Mario_Limonciello@Dell.com>; Darren Hart
> <dvhart@infradead.org>; Andy Shevchenko <andy@infradead.org>
> Cc: Edward O'Callaghan <quasisec@google.com>; Hans de Goede
> <hdegoede@redhat.com>; platform-driver-x86@vger.kernel.org; linux-
> kernel@vger.kernel.org
> Subject: Re: [PATCH] dell-smbios: fix string overflow
> 
> Hi,
> 
> I recommend using "platform/x86: dell-smbios:" in commit header.
> 
> On 11/08/2017 04:08 AM, Arnd Bergmann wrote:
> > The new sysfs code overwrites two fixed-length character arrays
> > that are each one byte shorter than they need to be, to hold
> > the trailing \0:
> >
> > drivers/platform/x86/dell-smbios.c: In function 'build_tokens_sysfs':
> > drivers/platform/x86/dell-smbios.c:494:42: error: 'sprintf' writing a terminating
> nul past the end of the destination [-Werror=format-overflow=]
> >     sprintf(buffer_location, "%04x_location",
> > drivers/platform/x86/dell-smbios.c:494:3: note: 'sprintf' output 14 bytes into a
> destination of size 13
> > drivers/platform/x86/dell-smbios.c:506:36: error: 'sprintf' writing a terminating
> nul past the end of the destination [-Werror=format-overflow=]
> >     sprintf(buffer_value, "%04x_value",
> > drivers/platform/x86/dell-smbios.c:506:3: note: 'sprintf' output 11 bytes into a
> destination of size 10
> Don't need to include the error log in commit message. Just explaining
> the issue is good enough.
> >
> > This changes it to just use kasprintf(), which always gets it right.
> >
> > Fixes: 33b9ca1e53b4 ("platform/x86: dell-smbios: Add a sysfs interface for
> SMBIOS tokens")
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > ---
> >   drivers/platform/x86/dell-smbios.c | 12 ++++--------
> >   1 file changed, 4 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/platform/x86/dell-smbios.c b/drivers/platform/x86/dell-
> smbios.c
> > index d99edd803c19..6a60db515bda 100644
> > --- a/drivers/platform/x86/dell-smbios.c
> > +++ b/drivers/platform/x86/dell-smbios.c
> > @@ -463,8 +463,6 @@ static struct platform_driver platform_driver = {
> >
> >   static int build_tokens_sysfs(struct platform_device *dev)
> >   {
> > -	char buffer_location[13];
> > -	char buffer_value[10];
> >   	char *location_name;
> >   	char *value_name;
> >   	size_t size;
> > @@ -491,9 +489,8 @@ static int build_tokens_sysfs(struct platform_device
> *dev)
> >   		if (da_tokens[i].tokenID == 0)
> >   			continue;
> >   		/* add location */
> > -		sprintf(buffer_location, "%04x_location",
> > -			da_tokens[i].tokenID);
> > -		location_name = kstrdup(buffer_location, GFP_KERNEL);
> > +		location_name = kasprintf(GFP_KERNEL, "%04x_location",
> > +					  da_tokens[i].tokenID);
> >   		if (location_name == NULL)
> >   			goto out_unwind_strings;
> >   		sysfs_attr_init(&token_location_attrs[i].attr);
> > @@ -503,9 +500,8 @@ static int build_tokens_sysfs(struct platform_device
> *dev)
> >   		token_attrs[j++] = &token_location_attrs[i].attr;
> >
> >   		/* add value */
> > -		sprintf(buffer_value, "%04x_value",
> > -			da_tokens[i].tokenID);
> > -		value_name = kstrdup(buffer_value, GFP_KERNEL);
> > +		value_name = kasprintf(GFP_KERNEL, "%04x_value",
> > +				       da_tokens[i].tokenID);
> >   		if (value_name == NULL)
> >   			goto loop_fail_create_value;
> >   		sysfs_attr_init(&token_value_attrs[i].attr);
> 
> --

Arnd,

Assuming Darren will do the fixup for title and message as recommended by 
Sathyanarayanan before committing:
Acked-by: Mario Limonciello <mario.limonciello@dell.com>

Thanks, for the fix.  For my own information and improvement, would you 
share how you caught that?  Just added "-Werror=format-overflow=" to CFLAGS?
I wasn't seeing the compile errors with default flags in my own testing, so I'd like 
to make sure I'm doing better testing in the future.

Re: [PATCH] dell-smbios: fix string overflow

[Andy Shevchenko]

On Wed, Nov 8, 2017 at 8:30 PM,  <Mario.Limonciello@dell.com> wrote:

>> I recommend using "platform/x86: dell-smbios:" in commit header.

While we (maintainers) are fixing this manually, it would be better if
contributors will do this themselves :-)

>> On 11/08/2017 04:08 AM, Arnd Bergmann wrote:
>> > The new sysfs code overwrites two fixed-length character arrays
>> > that are each one byte shorter than they need to be, to hold
>> > the trailing \0:
>> >
>> > drivers/platform/x86/dell-smbios.c: In function 'build_tokens_sysfs':
>> > drivers/platform/x86/dell-smbios.c:494:42: error: 'sprintf' writing a terminating
>> nul past the end of the destination [-Werror=format-overflow=]
>> >     sprintf(buffer_location, "%04x_location",
>> > drivers/platform/x86/dell-smbios.c:494:3: note: 'sprintf' output 14 bytes into a
>> destination of size 13
>> > drivers/platform/x86/dell-smbios.c:506:36: error: 'sprintf' writing a terminating
>> nul past the end of the destination [-Werror=format-overflow=]
>> >     sprintf(buffer_value, "%04x_value",
>> > drivers/platform/x86/dell-smbios.c:506:3: note: 'sprintf' output 11 bytes into a
>> destination of size 10
>> Don't need to include the error log in commit message. Just explaining
>> the issue is good enough.
>> >
>> > This changes it to just use kasprintf(), which always gets it right.

Good catch followed by a fix!

> Assuming Darren will do the fixup for title and message as recommended by
> Sathyanarayanan before committing:
> Acked-by: Mario Limonciello <mario.limonciello@dell.com>

> Thanks, for the fix.  For my own information and improvement, would you
> share how you caught that?  Just added "-Werror=format-overflow=" to CFLAGS?

> I wasn't seeing the compile errors with default flags in my own testing, so I'd like
> to make sure I'm doing better testing in the future.

gcc7 by its default [1], though you need to revert [2].

And always good to remember

% make W=1

which implies some warning, W=2 a lot more.

[1]: http://patches.linaro.org/cover/107779/

[2]: commit bd664f6b3e376a8ef4990f87d08271cc2d01ba9a
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed Jul 12 19:25:47 2017 -0700

   disable new gcc-7.1.1 warnings for now


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] dell-smbios: fix string overflow

[Arnd Bergmann]

On Wed, Nov 8, 2017 at 7:22 PM, sathyanarayanan kuppuswamy
<sathyanarayanan.kuppuswamy@linux.intel.com> wrote:
> Hi,
>
> I recommend using "platform/x86: dell-smbios:" in commit header.

Ok, noted. I usually try to follow the lines for each maintainer, but
I'm not always
keeping track of each one, sorry.

> On 11/08/2017 04:08 AM, Arnd Bergmann wrote:
>>
>> The new sysfs code overwrites two fixed-length character arrays
>> that are each one byte shorter than they need to be, to hold
>> the trailing \0:
>>
>> drivers/platform/x86/dell-smbios.c: In function 'build_tokens_sysfs':
>> drivers/platform/x86/dell-smbios.c:494:42: error: 'sprintf' writing a
>> terminating nul past the end of the destination [-Werror=format-overflow=]
>>     sprintf(buffer_location, "%04x_location",
>> drivers/platform/x86/dell-smbios.c:494:3: note: 'sprintf' output 14 bytes
>> into a destination of size 13
>> drivers/platform/x86/dell-smbios.c:506:36: error: 'sprintf' writing a
>> terminating nul past the end of the destination [-Werror=format-overflow=]
>>     sprintf(buffer_value, "%04x_value",
>> drivers/platform/x86/dell-smbios.c:506:3: note: 'sprintf' output 11 bytes
>> into a destination of size 10
>
> Don't need to include the error log in commit message. Just explaining the
> issue is good enough.

I always include the messages I get, it helps a lot when you run into a related
problem and find it in either the git log or using google search.

It's particularly useful when patches that introduce warnings get backported
to stable kernels.

      Arnd

Re: [PATCH] dell-smbios: fix string overflow

[Arnd Bergmann]

On Wed, Nov 8, 2017 at 8:03 PM, Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> On Wed, Nov 8, 2017 at 8:30 PM,  <Mario.Limonciello@dell.com> wrote:
>
> % make W=1
>
> which implies some warning, W=2 a lot more.
>
> [1]: http://patches.linaro.org/cover/107779/
>
> [2]: commit bd664f6b3e376a8ef4990f87d08271cc2d01ba9a
> Author: Linus Torvalds <torvalds@linux-foundation.org>
> Date:   Wed Jul 12 19:25:47 2017 -0700
>
>    disable new gcc-7.1.1 warnings for now

I have reverted that patch locally and this is the first time I
actually hit a warning
since it landed, but that reminds me that I should check whether all my
workarounds have landed in mainline and we are ready to turn it on globally
again.

     Arnd

Re: [PATCH] dell-smbios: fix string overflow

[Darren Hart]

On Wed, Nov 08, 2017 at 01:08:39PM +0100, Arnd Bergmann wrote:
> The new sysfs code overwrites two fixed-length character arrays
> that are each one byte shorter than they need to be, to hold
> the trailing \0:
> 
> drivers/platform/x86/dell-smbios.c: In function 'build_tokens_sysfs':
> drivers/platform/x86/dell-smbios.c:494:42: error: 'sprintf' writing a terminating nul past the end of the destination [-Werror=format-overflow=]
>    sprintf(buffer_location, "%04x_location",
> drivers/platform/x86/dell-smbios.c:494:3: note: 'sprintf' output 14 bytes into a destination of size 13
> drivers/platform/x86/dell-smbios.c:506:36: error: 'sprintf' writing a terminating nul past the end of the destination [-Werror=format-overflow=]
>    sprintf(buffer_value, "%04x_value",
> drivers/platform/x86/dell-smbios.c:506:3: note: 'sprintf' output 11 bytes into a destination of size 10
> 
> This changes it to just use kasprintf(), which always gets it right.
> 
> Fixes: 33b9ca1e53b4 ("platform/x86: dell-smbios: Add a sysfs interface for SMBIOS tokens")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>


Queued, thanks Arnd.

Yes, please keep the error messages. Costs us nothing and can be useful to have.

I corrected the prefix as noted, and added the details of the gcc and reverted
patch for reproducer context.

-- 
Darren Hart
VMware Open Source Technology Center

Re: [PATCH] dell-smbios: fix string overflow

[Pali Rohár]

On Wednesday 08 November 2017 13:08:39 Arnd Bergmann wrote:
> The new sysfs code overwrites two fixed-length character arrays
> that are each one byte shorter than they need to be, to hold
> the trailing \0:
> 
> drivers/platform/x86/dell-smbios.c: In function 'build_tokens_sysfs':
> drivers/platform/x86/dell-smbios.c:494:42: error: 'sprintf' writing a terminating nul past the end of the destination [-Werror=format-overflow=]
>    sprintf(buffer_location, "%04x_location",
> drivers/platform/x86/dell-smbios.c:494:3: note: 'sprintf' output 14 bytes into a destination of size 13
> drivers/platform/x86/dell-smbios.c:506:36: error: 'sprintf' writing a terminating nul past the end of the destination [-Werror=format-overflow=]
>    sprintf(buffer_value, "%04x_value",
> drivers/platform/x86/dell-smbios.c:506:3: note: 'sprintf' output 11 bytes into a destination of size 10
> 
> This changes it to just use kasprintf(), which always gets it right.
> 
> Fixes: 33b9ca1e53b4 ("platform/x86: dell-smbios: Add a sysfs interface for SMBIOS tokens")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Reviewed-by: Pali Rohár <pali.rohar@gmail.com>

> ---
>  drivers/platform/x86/dell-smbios.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/platform/x86/dell-smbios.c b/drivers/platform/x86/dell-smbios.c
> index d99edd803c19..6a60db515bda 100644
> --- a/drivers/platform/x86/dell-smbios.c
> +++ b/drivers/platform/x86/dell-smbios.c
> @@ -463,8 +463,6 @@ static struct platform_driver platform_driver = {
>  
>  static int build_tokens_sysfs(struct platform_device *dev)
>  {
> -	char buffer_location[13];
> -	char buffer_value[10];
>  	char *location_name;
>  	char *value_name;
>  	size_t size;
> @@ -491,9 +489,8 @@ static int build_tokens_sysfs(struct platform_device *dev)
>  		if (da_tokens[i].tokenID == 0)
>  			continue;
>  		/* add location */
> -		sprintf(buffer_location, "%04x_location",
> -			da_tokens[i].tokenID);
> -		location_name = kstrdup(buffer_location, GFP_KERNEL);
> +		location_name = kasprintf(GFP_KERNEL, "%04x_location",
> +					  da_tokens[i].tokenID);
>  		if (location_name == NULL)
>  			goto out_unwind_strings;
>  		sysfs_attr_init(&token_location_attrs[i].attr);
> @@ -503,9 +500,8 @@ static int build_tokens_sysfs(struct platform_device *dev)
>  		token_attrs[j++] = &token_location_attrs[i].attr;
>  
>  		/* add value */
> -		sprintf(buffer_value, "%04x_value",
> -			da_tokens[i].tokenID);
> -		value_name = kstrdup(buffer_value, GFP_KERNEL);
> +		value_name = kasprintf(GFP_KERNEL, "%04x_value",
> +				       da_tokens[i].tokenID);
>  		if (value_name == NULL)
>  			goto loop_fail_create_value;
>  		sysfs_attr_init(&token_value_attrs[i].attr);

-- 
Pali Rohár
pali.rohar@gmail.com