From 964417a5d4a06614ef7fb3ae69bb17c91a2dc016 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Thu, 23 Jan 2025 17:21:30 -0800 Subject: [PATCH] tools: ynl: c: correct reverse decode of empty attrs netlink reports which attribute was incorrect by sending back an attribute offset. Offset points to the address of struct nlattr, but to interpret the type we also need the nesting path. Attribute IDs have different meaning in different nests of the same message. Correct the condition for "is the offset within current attribute". ynl_attr_data_len() does not include the attribute header, so the end offset was off by 4 bytes. This means that we'd always skip over flags and empty nests. The devmem tests, for example, issues an invalid request with empty queue nests, resulting in the following error: YNL failed: Kernel error: missing attribute: .queues.ifindex The message is incorrect, "queues" nest does not have an "ifindex" attribute defined. With this fix we decend correctly into the nest: YNL failed: Kernel error: missing attribute: .queues.id Fixes: 86878f14d71a ("tools: ynl: user space helpers") Reviewed-by: Donald Hunter Link: https://patch.msgid.link/20250124012130.1121227-1-kuba@kernel.org Signed-off-by: Jakub Kicinski --- tools/net/ynl/lib/ynl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/net/ynl/lib/ynl.c b/tools/net/ynl/lib/ynl.c index e16cef160bc2c..ce32cb35007d6 100644 --- a/tools/net/ynl/lib/ynl.c +++ b/tools/net/ynl/lib/ynl.c @@ -95,7 +95,7 @@ ynl_err_walk(struct ynl_sock *ys, void *start, void *end, unsigned int off, ynl_attr_for_each_payload(start, data_len, attr) { astart_off = (char *)attr - (char *)start; - aend_off = astart_off + ynl_attr_data_len(attr); + aend_off = (char *)ynl_attr_data_end(attr) - (char *)start; if (aend_off <= off) continue; -- 2.50.1