[PATCH] Compile-time check re world-writeable module params

From: Alexey Dobriyan
Date: Sun Oct 29 2006 - 19:00:58 EST


One of mistakes module_param() user can make is to supply default value
of module parameter as the last argument. module_param() accepts
permissions instead. If default value is, say, 3 (-------wx), parameter
becomes world-writeable.

So far, the only remedy was to apply grep(1) and read drivers submitted
to -mm. BTDT.

With this patch applied, compiler will finally do some job.

*) bounds checking on permissions
*) world-writeable bit checking on permissions
*) compile breakage if checks trigger

First version of this check (only "& 2" part) directly caught 4 out of 7
places during my last grep.

Subject: Neverending module_param() bugs
[X] drivers/acpi/sbs.c:101:module_param(capacity_mode, int, CAPACITY_UNIT);
[X] drivers/acpi/sbs.c:102:module_param(update_mode, int, UPDATE_MODE);
[ ] drivers/acpi/sbs.c:103:module_param(update_info_mode, int, UPDATE_INFO_MODE);
[ ] drivers/acpi/sbs.c:104:module_param(update_time, int, UPDATE_TIME);
[ ] drivers/acpi/sbs.c:105:module_param(update_time2, int, UPDATE_TIME2);
[X] drivers/char/watchdog/sbc8360.c:203:module_param(timeout, int, 27);
[X] drivers/media/video/tuner-simple.c:13:module_param(offset, int, 0666);

Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---

include/linux/moduleparam.h | 3 +++
1 file changed, 3 insertions(+)

--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -63,6 +63,9 @@ struct kparam_array
not there, read bits mean it's readable, write bits mean it's
writable. */
#define __module_param_call(prefix, name, set, get, arg, perm) \
+ /* Default value instead of permissions? */ \
+ static int __param_perm_check_##name __attribute__((unused)) = \
+ BUILD_BUG_ON_ZERO((perm) < 0 || (perm) > 0777 || ((perm) & 2)); \
static char __param_str_##name[] = prefix #name; \
static struct kernel_param const __param_##name \
__attribute_used__ \

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