Re: [PATCH] virtio-blk: make the queue depth configurable

On Wed, Mar 19, 2014 at 05:07:50PM +1030, Rusty Russell wrote:

Joe Perches [off-list ref] writes:

quoted

On Sun, 2014-03-16 at 22:00 -0700, Joe Perches wrote:

quoted

On Mon, 2014-03-17 at 14:25 +1030, Rusty Russell wrote:

quoted

Erk, our tests are insufficient.  Testbuilding an allmodconfig with this
now:

Good idea.

quoted

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h

[]

quoted

@@ -188,6 +188,9 @@ struct kparam_array
 	/* Default value instead of permissions? */			\
 	static int __param_perm_check_##name __attribute__((unused)) =	\
 	BUILD_BUG_ON_ZERO((perm) < 0 || (perm) > 0777 || ((perm) & 2))	\
+	/* User perms >= group perms >= other perms. */			\
+	+ BUILD_BUG_ON_ZERO(((perm) >> 6) < (((perm) >> 3) & 7))	\
+	+ BUILD_BUG_ON_ZERO((((perm) >> 3) & 7) < ((perm) & 7))		\
 	+ BUILD_BUG_ON_ZERO(sizeof(""prefix) > MAX_PARAM_PREFIX_LEN);	\
 	static const char __param_str_##name[] = prefix #name;		\
 	static struct kernel_param __moduleparam_const __param_##name	\

It might make sense to separate this octal permissions
test into a new macro for other checks in macros like
CLASS_ATTR, DEVICE_ATTR, SENSOR_ATTR and SENSOR_ATTR_2.

OK, I took your bikeshed and re-painted it below.

quoted

#define VERIFY_OCTAL_PERMISSIONS(perms)					\
({									\
	if (__builtin_constant_p(perms)) {				\
		BUILD_BUG_ON((perms) < 0);				\
		BUILD_BUG_ON((perms) > 0777);				\
		/* User perms >= group perms >= other perms */		\
		BUILD_BUG_ON(((perms) >> 6) < (((perms) >> 3) & 7));	\
		BUILD_BUG_ON((((perms) >> 3) & 7) < ((perms) & 7));	\
	}								\
	;								\
})

Subject: VERIFY_OCTAL_PERMISSIONS: stricter checking for sysfs perms.

Summary of http://lkml.org/lkml/2014/3/14/363 :

  Ted: module_param(queue_depth, int, 444)
  Joe: 0444!
  Rusty: User perms >= group perms >= other perms?
  Joe: CLASS_ATTR, DEVICE_ATTR, SENSOR_ATTR and SENSOR_ATTR_2?

Side effect of stricter permissions means removing the unnecessary
S_IFREG from drivers/pci/slot.c.

Suggested-by: Joe Perches <joe@perches.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Rusty Russell <redacted>

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>