[PROBLEM linux-next]

[Jonas Gorski]

On Sun, 7 Jul 2024 at 09:38, Rafał Miłecki <rafal at milecki.pl> wrote:
>
> Some more descriptive subject would be nice :)
>
>
> On 7.07.2024 02:10, Mirsad Todorovac wrote:
> > In file included from ./include/asm-generic/bug.h:22,
> >                   from ./arch/x86/include/asm/bug.h:87,
> >                   from ./include/linux/bug.h:5,
> >                   from ./include/linux/fortify-string.h:6,
> >                   from ./include/linux/string.h:374,
> >                   from ./arch/x86/include/asm/page_32.h:18,
> >                   from ./arch/x86/include/asm/page.h:14,
> >                   from ./arch/x86/include/asm/processor.h:20,
> >                   from ./arch/x86/include/asm/timex.h:5,
> >                   from ./include/linux/timex.h:67,
> >                   from ./include/linux/time32.h:13,
> >                   from ./include/linux/time.h:60,
> >                   from ./include/linux/stat.h:19,
> >                   from ./include/linux/module.h:13,
> >                   from drivers/mtd/mtdpart.c:10:
> > drivers/mtd/mtdpart.c: In function ‘parse_mtd_partitions’:
> > drivers/mtd/mtdpart.c:693:34: error: ‘%s’ directive argument is null [-Werror=format-overflow=]
> >    693 |                         pr_debug("%s: got parser %s\n", master->name,
> >        |                                  ^~~~~~~~~~~~~~~~~~~~~
> > ./include/linux/printk.h:376:21: note: in definition of macro ‘pr_fmt’
> >    376 | #define pr_fmt(fmt) fmt
> >        |                     ^~~
> > ./include/linux/dynamic_debug.h:248:9: note: in expansion of macro ‘__dynamic_func_call_cls’
> >    248 |         __dynamic_func_call_cls(__UNIQUE_ID(ddebug), cls, fmt, func, ##__VA_ARGS__)
> >        |         ^~~~~~~~~~~~~~~~~~~~~~~
> > ./include/linux/dynamic_debug.h:250:9: note: in expansion of macro ‘_dynamic_func_call_cls’
> >    250 |         _dynamic_func_call_cls(_DPRINTK_CLASS_DFLT, fmt, func, ##__VA_ARGS__)
> >        |         ^~~~~~~~~~~~~~~~~~~~~~
> > ./include/linux/dynamic_debug.h:269:9: note: in expansion of macro ‘_dynamic_func_call’
> >    269 |         _dynamic_func_call(fmt, __dynamic_pr_debug,             \
> >        |         ^~~~~~~~~~~~~~~~~~
> > ./include/linux/printk.h:610:9: note: in expansion of macro ‘dynamic_pr_debug’
> >    610 |         dynamic_pr_debug(fmt, ##__VA_ARGS__)
> >        |         ^~~~~~~~~~~~~~~~
> > drivers/mtd/mtdpart.c:693:25: note: in expansion of macro ‘pr_debug’
> >    693 |                         pr_debug("%s: got parser %s\n", master->name,
> >        |                         ^~~~~~~~
> > drivers/mtd/mtdpart.c:693:50: note: format string is defined here
> >    693 |                         pr_debug("%s: got parser %s\n", master->name,
> >        |                                                  ^~
> >
> > Offending commit is 5b644aa012f67.
>
> Actually it goes back to 2015 to the commit 8e2c992b59fc ("mtd: mtdpart: add debug prints to partition parser.").
>
>
> > Proposed non-intrusive fix resolves the warning/error, but I could not test the code.
> > (I don't have the physical device.)
> >
> > -----------------><------------------------------------------
> > diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
> > index 6811a714349d..81665d67ed2d 100644
> > --- a/drivers/mtd/mtdpart.c
> > +++ b/drivers/mtd/mtdpart.c
> > @@ -691,7 +691,7 @@ int parse_mtd_partitions(struct mtd_info *master, const char *const *types,
> >                          if (!parser && !request_module("%s", *types))
> >                                  parser = mtd_part_parser_get(*types);
> >                          pr_debug("%s: got parser %s\n", master->name,
> > -                               parser ? parser->name : NULL);
> > +                               parser ? parser->name : "(null"));
> >                          if (!parser)
> >                                  continue;
> >                          ret = mtd_part_do_parse(parser, master, &pparts, data);
> >
> >
> > Hope this helps.
>
> I'd say it's simple enough to send patch without actual hw testing.

Though the kernel's vsprintf will already handle NULL pointers and
print "(null)" [1], so I'm not sure if this is an actual improvement.

The only way this can be NULL though is if the request_module()
failed, so maybe a proper error message would be better here instead
of an obscure "got parser (null)". You don't even know which type
wasn't available. E.g. pr_debug("%: no parser for type %s
available\n", master->name, *types).

[1] https://elixir.bootlin.com/linux/latest/source/lib/vsprintf.c#L696

Best Regards,
Jonas