[PATCH v2 net-next 1/2] tools: ynl: check for null ptr on dump free

Static analysis detected code paths where freeing a dump list after early
errors when creating the corresponding dump list like in ynl_exec_dump()
can result in a null pointer dereference since the first node in the
ynl_dump_state would still be zero initialized. To prevent this potential
problem updated the ynl c generation script to check for a NULL pointer
before continuing to free the nodes in a dump list.

Signed-off-by: Thaison Phan <[email protected]>
---
v1 -> v2: Updated to check for NULL outside of while loop to make intent of
check more clear since there can not be a NULL while iterating the list
(Suggested by Jakub Kicinski)

v1:
https://lore.kernel.org/netdev/[email protected]/

 tools/net/ynl/pyynl/ynl_gen_c.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/net/ynl/pyynl/ynl_gen_c.py b/tools/net/ynl/pyynl/ynl_gen_c.py
index cdc3646f2642..95502dbaec94 100755
--- a/tools/net/ynl/pyynl/ynl_gen_c.py
+++ b/tools/net/ynl/pyynl/ynl_gen_c.py
@@ -2747,6 +2747,9 @@ def print_dump_type_free(ri):
     ri.cw.block_start()
     ri.cw.p(f"{sub_type} *next = rsp;")
     ri.cw.nl()
+    ri.cw.p('if (!next)')
+    ri.cw.p('return;')
+    ri.cw.nl()
     ri.cw.block_start(line='while ((void *)next != YNL_LIST_END)')
     _free_type_members_iter(ri, ri.struct['reply'])
     ri.cw.p('rsp = next;')
-- 
2.55.0.654.g21b8a5bc05-goog