diff mbox series

[07/12] driver/char: use correct format characters

Message ID 20220609221702.347522-8-morbo@google.com (mailing list archive)
State New, archived
Headers show
Series Clang -Wformat warning fixes | expand

Commit Message

Bill Wendling June 9, 2022, 10:16 p.m. UTC
From: Bill Wendling <isanbard@gmail.com>

When compiling with -Wformat, clang emits the following warnings:

drivers/char/mem.c:775:16: error: format string is not a string literal (potentially insecure) [-Werror,-Wformat-security]
                              NULL, devlist[minor].name);
                                    ^~~~~~~~~~~~~~~~~~~

Use a string literal for the format string.

Link: https://github.com/ClangBuiltLinux/linux/issues/378
Signed-off-by: Bill Wendling <isanbard@gmail.com>
---
 drivers/char/mem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Greg KH June 10, 2022, 5:18 a.m. UTC | #1
On Thu, Jun 09, 2022 at 10:16:26PM +0000, Bill Wendling wrote:
> From: Bill Wendling <isanbard@gmail.com>

Why isn't that matching your From: line in the email?

> 
> When compiling with -Wformat, clang emits the following warnings:

Is that ever a default build option for the kernel?

> 
> drivers/char/mem.c:775:16: error: format string is not a string literal (potentially insecure) [-Werror,-Wformat-security]
>                               NULL, devlist[minor].name);
>                                     ^~~~~~~~~~~~~~~~~~~
> 
> Use a string literal for the format string.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/378
> Signed-off-by: Bill Wendling <isanbard@gmail.com>
> ---
>  drivers/char/mem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> index 84ca98ed1dad..32d821ba9e4d 100644
> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -772,7 +772,7 @@ static int __init chr_dev_init(void)
>  			continue;
>  
>  		device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
> -			      NULL, devlist[minor].name);
> +			      NULL, "%s", devlist[minor].name);

Please explain how this static string can ever be user controlled.

thanks,

greg k-h
Bill Wendling June 13, 2022, 6:40 p.m. UTC | #2
On Thu, Jun 9, 2022 at 10:18 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Thu, Jun 09, 2022 at 10:16:26PM +0000, Bill Wendling wrote:
> > From: Bill Wendling <isanbard@gmail.com>
>
> Why isn't that matching your From: line in the email?
>
There must be something wrong with my .gitconfig file. I"ll check into it.

> >
> > When compiling with -Wformat, clang emits the following warnings:
>
> Is that ever a default build option for the kernel?
>
We want to enable -Wformat for clang. I believe that these specific
warnings have been disabled, but I'm confused as to why, because
they're valid warnings. When I compiled with the warning enabled,
there were only a few (12) places that needed changes, so thought that
patches would be a nice cleanup, even though the warning itself is
disabled.

> > drivers/char/mem.c:775:16: error: format string is not a string literal (potentially insecure) [-Werror,-Wformat-security]
> >                               NULL, devlist[minor].name);
> >                                     ^~~~~~~~~~~~~~~~~~~
> >
> > Use a string literal for the format string.
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/378
> > Signed-off-by: Bill Wendling <isanbard@gmail.com>
> > ---
> >  drivers/char/mem.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> > index 84ca98ed1dad..32d821ba9e4d 100644
> > --- a/drivers/char/mem.c
> > +++ b/drivers/char/mem.c
> > @@ -772,7 +772,7 @@ static int __init chr_dev_init(void)
> >                       continue;
> >
> >               device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
> > -                           NULL, devlist[minor].name);
> > +                           NULL, "%s", devlist[minor].name);
>
> Please explain how this static string can ever be user controlled.
>
All someone would need to do is accidentally insert an errant '%' in
one of the strings for this function call to perform unexpected
actions---at the very least reading memory that's not allocated and
may contain garbage, thereby decreasing performance and possibly
overrunning some buffer. Perhaps in this specific scenario it's
unlikely, but "device_create()" is used in a lot more places than
here. This patch is a general code cleanup.

-bw
diff mbox series

Patch

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 84ca98ed1dad..32d821ba9e4d 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -772,7 +772,7 @@  static int __init chr_dev_init(void)
 			continue;
 
 		device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
-			      NULL, devlist[minor].name);
+			      NULL, "%s", devlist[minor].name);
 	}
 
 	return tty_init();