[PATCH 5.10 578/717] dyndbg: fix use before null check

Greg Kroah-Hartman
2020-12-28T14:28:56Z

From: Jim Cromie <jim.cromie@gmail.com>

commit 3577afb0052fca65e67efdfc8e0859bb7bac87a6 upstream.

In commit a2d375eda771 ("dyndbg: refine export, rename to
dynamic_debug_exec_queries()"), a string is copied before checking it
isn't NULL. Fix this, report a usage/interface error, and return the
proper error code.

Fixes: a2d375eda771 ("dyndbg: refine export, rename to dynamic_debug_exec_queries()")
Cc: stable@vger.kernel.org
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20201209183625.2432329-1-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
lib/dynamic_debug.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -561,9 +561,14 @@ static int ddebug_exec_queries(char *que
int dynamic_debug_exec_queries(const char *query, const char *modname)
{
int rc;
- char *qry = kstrndup(query, PAGE_SIZE, GFP_KERNEL);
+ char *qry; /* writable copy of query */

- if (!query)
+ if (!query) {
+ pr_err("non-null query/command string expected\n");
+ return -EINVAL;
+ }
+ qry = kstrndup(query, PAGE_SIZE, GFP_KERNEL);
+ if (!qry)
return -ENOMEM;

rc = ddebug_exec_queries(qry, modname);