Re: [PATCH] scsi: core: Safe warning about bad dev info string

[Chris Down]

Petr Mladek writes:
> Both "model" and "strflags" are passed to "%s" even when one or both
> are NULL.
>
> It is safe because vsprintf() would detect the NULL pointer and print
> "(null)". But it is a kernel-specific feature and compiler warns
> about it:
>
> <warning>
>   In file included from include/linux/kernel.h:19,
>                    from arch/x86/include/asm/percpu.h:27,
>                    from arch/x86/include/asm/current.h:6,
>                    from include/linux/sched.h:12,
>                    from include/linux/blkdev.h:5,
>                    from drivers/scsi/scsi_devinfo.c:3:
>   drivers/scsi/scsi_devinfo.c: In function 'scsi_dev_info_list_add_str':
> > > include/linux/printk.h:434:44: warning: '%s' directive argument is null [-Wformat-overflow=]
>     434 | #define printk(fmt, ...) printk_index_wrap(_printk, fmt, ##__VA_ARGS__)
>         |                                            ^
>   include/linux/printk.h:430:3: note: in definition of macro 'printk_index_wrap'
>     430 |   _p_func(_fmt, ##__VA_ARGS__);    \
>         |   ^~~~~~~
>   drivers/scsi/scsi_devinfo.c:551:4: note: in expansion of macro 'printk'
>     551 |    printk(KERN_ERR "%s: bad dev info string '%s' '%s'"
>         |    ^~~~~~
>   drivers/scsi/scsi_devinfo.c:552:14: note: format string is defined here
>     552 |           " '%s'\n", __func__, vendor, model,
>         |              ^~
> </warning>
>
> Do not rely on the kernel specific behavior and print the message a safe way.

Acked-by: Chris Down <chris@xxxxxxxxxxxxxx>

While I agree with the other thread that in reality this is ok, it's worth 
reducing the addition to LKP noise for now and worrying about that later.

Thanks!

> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Closes: https://lore.kernel.org/oe-kbuild-all/202401112002.AOjwMNM0-lkp@xxxxxxxxx/
> Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
> ---
> Note: The patch is only compile tested.
>
> drivers/scsi/scsi_devinfo.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/scsi/scsi_devinfo.c b/drivers/scsi/scsi_devinfo.c
> index 3fcaf10a9dfe..ba7237e83863 100644
> --- a/drivers/scsi/scsi_devinfo.c
> +++ b/drivers/scsi/scsi_devinfo.c
> @@ -551,9 +551,9 @@ static int scsi_dev_info_list_add_str(char *dev_list)
> 		if (model)
> 			strflags = strsep(&next, next_check);
> 		if (!model || !strflags) {
> -			printk(KERN_ERR "%s: bad dev info string '%s' '%s'"
> -			       " '%s'\n", __func__, vendor, model,
> -			       strflags);
> +			pr_err("%s: bad dev info string '%s' '%s' '%s'\n",
> +			       __func__, vendor, model ? model : "",
> +			       strflags ? strflags : "");
> 			res = -EINVAL;
> 		} else
> 			res = scsi_dev_info_list_add(0 /* compatible */, vendor,
> --
> 2.43.0