[PATCH v1 1/1] genirq: Bump the size of the local variable for sprintf()

[PATCH v1 1/1] genirq: Bump the size of the local variable for sprintf()

[Andy Shevchenko]

GCC is not happy about sprintf() call on a buffer that might be too small for
the given formatting string.

kernel/irq/debugfs.c:233:26: warning: 'sprintf' may write a terminating nul past the end of the destination [-Wformat-overflow=]

Fix this by bumping the size of the local variable for sprintf().

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202505151057.xbyXAbEn-lkp@intel.com/
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 kernel/irq/debugfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/irq/debugfs.c b/kernel/irq/debugfs.c
index 3d6a5b3cfaf3..3527defd2890 100644
--- a/kernel/irq/debugfs.c
+++ b/kernel/irq/debugfs.c
@@ -225,7 +225,7 @@ void irq_debugfs_copy_devname(int irq, struct device *dev)
 
 void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *desc)
 {
-	char name [10];
+	char name [12];
 
 	if (!irq_dir || !desc || desc->debugfs_file)
 		return;
-- 
2.47.2

[tip: irq/core] genirq: Bump the size of the local variable for sprintf()

[tip-bot2 for Andy Shevchenko]

The following commit has been merged into the irq/core branch of tip:

Commit-ID:     a4a39c81e1043b153bde3ef5cb3cf94222ffd918
Gitweb:        https://git.kernel.org/tip/a4a39c81e1043b153bde3ef5cb3cf94222ffd918
Author:        Andy Shevchenko <andriy.shevchenko@linux.intel.com>
AuthorDate:    Thu, 15 May 2025 11:55:16 +03:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 15 May 2025 16:28:09 +02:00

genirq: Bump the size of the local variable for sprintf()

GCC is not happy about a sprintf() call on a buffer that might be too small
for the given formatting string.

kernel/irq/debugfs.c:233:26: warning: 'sprintf' may write a terminating nul past the end of the destination [-Wformat-overflow=]

Fix this by bumping the size of the local variable for sprintf().

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250515085516.2913290-1-andriy.shevchenko@linux.intel.com
Closes: https://lore.kernel.org/oe-kbuild-all/202505151057.xbyXAbEn-lkp@intel.com/
---
 kernel/irq/debugfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/irq/debugfs.c b/kernel/irq/debugfs.c
index 3d6a5b3..3527def 100644
--- a/kernel/irq/debugfs.c
+++ b/kernel/irq/debugfs.c
@@ -225,7 +225,7 @@ void irq_debugfs_copy_devname(int irq, struct device *dev)
 
 void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *desc)
 {
-	char name [10];
+	char name [12];
 
 	if (!irq_dir || !desc || desc->debugfs_file)
 		return;

Re: [PATCH v1 1/1] genirq: Bump the size of the local variable for sprintf()

[Jiri Slaby]

On 15. 05. 25, 10:55, Andy Shevchenko wrote:
> GCC is not happy about sprintf() call on a buffer that might be too small for
> the given formatting string.
> 
> kernel/irq/debugfs.c:233:26: warning: 'sprintf' may write a terminating nul past the end of the destination [-Wformat-overflow=]
> 
> Fix this by bumping the size of the local variable for sprintf().
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202505151057.xbyXAbEn-lkp@intel.com/
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>   kernel/irq/debugfs.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/irq/debugfs.c b/kernel/irq/debugfs.c
> index 3d6a5b3cfaf3..3527defd2890 100644
> --- a/kernel/irq/debugfs.c
> +++ b/kernel/irq/debugfs.c
> @@ -225,7 +225,7 @@ void irq_debugfs_copy_devname(int irq, struct device *dev)
>   
>   void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *desc)
>   {
> -	char name [10];
> +	char name [12];

The max irq is ~ 512000, if I am counting correctly, so 7 B should be 
actually enough for everybody ;).

But well, can we silence the warning in a better way? I doubt that...

>   
>   	if (!irq_dir || !desc || desc->debugfs_file)
>   		return;

-- 
js
suse labs

Re: [PATCH v1 1/1] genirq: Bump the size of the local variable for sprintf()

[Andy Shevchenko]

On Fri, May 16, 2025 at 06:45:04AM +0200, Jiri Slaby wrote:
> On 15. 05. 25, 10:55, Andy Shevchenko wrote:

...

> > -	char name [10];
> > +	char name [12];
> 
> The max irq is ~ 512000, if I am counting correctly, so 7 B should be
> actually enough for everybody ;).

GCC can't proved it. And FWIW, on current Debian unstable (GCC 14?) I can't
reproduce this. In any case this doesn't increase stack usage AFAICT, the array
already have reserved 12 or 16 bytes.

> But well, can we silence the warning in a better way? I doubt that...

With the above said, I think it's pretty much close to the best way.
But if you find anything better, I also would like to learn.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v1 1/1] genirq: Bump the size of the local variable for sprintf()

[Jiri Slaby]

On 16. 05. 25, 11:07, Andy Shevchenko wrote:
> On Fri, May 16, 2025 at 06:45:04AM +0200, Jiri Slaby wrote:
>> On 15. 05. 25, 10:55, Andy Shevchenko wrote:
> 
> ...
> 
>>> -	char name [10];
>>> +	char name [12];
>>
>> The max irq is ~ 512000, if I am counting correctly, so 7 B should be
>> actually enough for everybody ;).
> 
> GCC can't proved it. And FWIW, on current Debian unstable (GCC 14?) I can't
> reproduce this. In any case this doesn't increase stack usage AFAICT, the array
> already have reserved 12 or 16 bytes.

Yes, sure, I am not disputing the fix.

>> But well, can we silence the warning in a better way? I doubt that...
> 
> With the above said, I think it's pretty much close to the best way.
> But if you find anything better, I also would like to learn.

Perhaps next in row would be using snprintf(), but dunno if it's better 
at all.

-- 
js
suse labs

Re: [PATCH v1 1/1] genirq: Bump the size of the local variable for sprintf()

[Andy Shevchenko]

On Fri, May 16, 2025 at 12:23:17PM +0200, Jiri Slaby wrote:
> On 16. 05. 25, 11:07, Andy Shevchenko wrote:
> > On Fri, May 16, 2025 at 06:45:04AM +0200, Jiri Slaby wrote:
> > > On 15. 05. 25, 10:55, Andy Shevchenko wrote:

...

> > > > -	char name [10];
> > > > +	char name [12];
> > > 
> > > The max irq is ~ 512000, if I am counting correctly, so 7 B should be
> > > actually enough for everybody ;).
> > 
> > GCC can't proved it. And FWIW, on current Debian unstable (GCC 14?) I can't
> > reproduce this. In any case this doesn't increase stack usage AFAICT, the array
> > already have reserved 12 or 16 bytes.
> 
> Yes, sure, I am not disputing the fix.
> 
> > > But well, can we silence the warning in a better way? I doubt that...
> > 
> > With the above said, I think it's pretty much close to the best way.
> > But if you find anything better, I also would like to learn.
> 
> Perhaps next in row would be using snprintf(), but dunno if it's better at
> all.

Try it. I believe you will get the same result. The problem is not in 'n' or
'n'-less variant, the problem is that GCC can't prove the limits of the input
value.

-- 
With Best Regards,
Andy Shevchenko