param: initialize store function to NULL if not available.

I rebased Kees' 'param: do not set store func without write perm'
on top of my 'params: cleanup sysfs allocation'.  However, my patch
uses krealloc which doesn't zero memory, leaving .store unset.

Reported-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/params.c b/kernel/params.c
index 0af9b2c4e56c..bd65d136a470 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -648,6 +648,8 @@ static __modinit int add_sysfs_param(struct module_kobject *mk,
         /* Do not allow runtime DAC changes to make param writable. */
         if ((kp->perm & (S_IWUSR | S_IWGRP | S_IWOTH)) != 0)
                 mk->mp->attrs[mk->mp->num].mattr.store = param_attr_store;
+        else
+                mk->mp->attrs[mk->mp->num].mattr.store = NULL;
         mk->mp->attrs[mk->mp->num].mattr.attr.name = (char *)name;
         mk->mp->attrs[mk->mp->num].mattr.attr.mode = kp->perm;
         mk->mp->num++;