params: Fix potential memory leak in add_sysfs_param()

On allocation failure, it would fail to free the old attrs array which
was no longer referenced by anything (since it would free the old
module_param_attrs struct on the way out).

Comment the suspicious-looking krealloc() usage to explain why it *isn't*
actually buggy, despite looking like a classic realloc() usage bug.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/kernel/params.c b/kernel/params.c
index ed35345be536..53b958fcd639 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -613,10 +613,13 @@ static __modinit int add_sysfs_param(struct module_kobject *mk,
                        sizeof(*mk->mp) + sizeof(mk->mp->attrs[0]) * (num+1),
                        GFP_KERNEL);
         if (!new) {
-                kfree(mk->mp);
+                kfree(attrs);
                 err = -ENOMEM;
                 goto fail;
         }
+        /* Despite looking like the typical realloc() bug, this is safe.
+         * We *want* the old 'attrs' to be freed either way, and we'll store
+         * the new one in the success case. */
         attrs = krealloc(attrs, sizeof(new->grp.attrs[0])*(num+2), GFP_KERNEL);
         if (!attrs) {
                 err = -ENOMEM;