On Thu, Jun 9, 2022 at 10:18 PM Greg Kroah-Hartman
[off-list ref] wrote:

On Thu, Jun 09, 2022 at 10:16:26PM +0000, Bill Wendling wrote:

quoted

From: Bill Wendling <redacted>

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.

quoted

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.

quoted

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 <redacted>
---
 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