[PATCH 4.14 071/164] kdb: Fix handling of kallsyms_symbol_next() return value

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Thompson <daniel.thompson@xxxxxxxxxx>

commit c07d35338081d107e57cf37572d8cc931a8e32e2 upstream.

kallsyms_symbol_next() returns a boolean (true on success). Currently
kdb_read() tests the return value with an inequality that
unconditionally evaluates to true.

This is fixed in the obvious way and, since the conditional branch is
supposed to be unreachable, we also add a WARN_ON().

Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Signed-off-by: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/debug/kdb/kdb_io.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -350,7 +350,7 @@ poll_again:
 			}
 			kdb_printf("\n");
 			for (i = 0; i < count; i++) {
-				if (kallsyms_symbol_next(p_tmp, i) < 0)
+				if (WARN_ON(!kallsyms_symbol_next(p_tmp, i)))
 					break;
 				kdb_printf("%s ", p_tmp);
 				*(p_tmp + len) = '\0';