[OpenWrt-Devel] [PATCH uci 14/18] lua: fix memory leak in set method

[Petr Štetiar]

scan-build from clang version 9 has reported following issue:

 uci.c:624:12: warning: Potential leak of memory pointed to by 's'
       return luaL_error(L, "Cannot set an uci option to an empty table value");
              ^~~~~~~~~~

valgrind confirmed it on the supplied test case:

 ==31013== 8 bytes in 1 blocks are definitely lost in loss record 1 of 1
 ==31013==    by 0x56C49B9: strdup (strdup.c:42)

Signed-off-by: Petr Štetiar <ynezz at true.cz>
---
 lua/uci.c                                                  | 5 ++++-
 .../lua/test_cases/set_with_empty_table_doesnt_leak.lua    | 2 ++
 tests/cram/test_ucilua_testcases.t                         | 7 +++++++
 3 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 tests/cram/lua/test_cases/set_with_empty_table_doesnt_leak.lua

diff --git a/lua/uci.c b/lua/uci.c
index 42fe4b785901..a7aaad375c20 100644
--- a/lua/uci.c
+++ b/lua/uci.c
@@ -620,8 +620,11 @@ uci_lua_set(lua_State *L)
 	case 4:
 		/* Format: uci.set("p", "s", "o", "v") */
 		if (lua_istable(L, nargs)) {
-			if (lua_rawlen(L, nargs) < 1)
+			if (lua_rawlen(L, nargs) < 1) {
+				if (s)
+					free(s);
 				return luaL_error(L, "Cannot set an uci option to an empty table value");
+			}
 			lua_rawgeti(L, nargs, 1);
 			ptr.value = luaL_checkstring(L, -1);
 			lua_pop(L, 1);
diff --git a/tests/cram/lua/test_cases/set_with_empty_table_doesnt_leak.lua b/tests/cram/lua/test_cases/set_with_empty_table_doesnt_leak.lua
new file mode 100644
index 000000000000..83e91d3ab264
--- /dev/null
+++ b/tests/cram/lua/test_cases/set_with_empty_table_doesnt_leak.lua
@@ -0,0 +1,2 @@
+local c = uci.cursor(os.getenv("CONFIG_DIR"))
+print(pcall(c.set, c, "network", "lan", "dns", {}))
diff --git a/tests/cram/test_ucilua_testcases.t b/tests/cram/test_ucilua_testcases.t
index 279dfce9422a..6a0216b3ded8 100644
--- a/tests/cram/test_ucilua_testcases.t
+++ b/tests/cram/test_ucilua_testcases.t
@@ -8,3 +8,10 @@ check that changes method doesnt leak memory:
   $ cp -R "$TESTDIR/config" .
   $ export CONFIG_DIR=$(pwd)/config
   $ ucilua $TESTDIR/lua/test_cases/changes_doesnt_leak.lua
+
+check that set method with empty table value doesn't leak memory:
+
+  $ cp -R "$TESTDIR/config" .
+  $ export CONFIG_DIR=$(pwd)/config
+  $ ucilua $TESTDIR/lua/test_cases/set_with_empty_table_doesnt_leak.lua
+  false\tCannot set an uci option to an empty table value (esc)

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