On Fri 2024-01-12 10:22:44, Geert Uytterhoeven wrote: > Hi Petr, > > On Thu, Jan 11, 2024 at 5:26 PM Petr Mladek <pmladek@xxxxxxxx> wrote: > > 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. > > > > 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 : ""); > > Do we really want to make this change? > The kernel's vsprintf() implementation has supported NULL pointers > since forever, and lots of code relies on that behavior. Yeah, it was safe even in the first git commit. And it was probably safe long before. Well, I can't find easily how much code relies on this. I would personally do not rely on it when writing new code. > Perhaps this warning can be disabled instead? IMHO, it is not a good idea to disable the warning. I believe that it checks also other scenarios and can find real problems. Also I think that compilers are getting more and more "clever". So keeping the "suspicious" code might be fighting with windmills. Best Regards, Petr
