[libnftnl PATCH] src: Fix for reading garbage in nftnl_chain getters

[libnftnl PATCH] src: Fix for reading garbage in nftnl_chain getters

[Phil Sutter]

In {s,u}{32,64} type getters nftnl_assert() is called to make sure
returned data length matches expectations. Therefore all attributes must
set data_len, which NFTNL_CHAIN_DEVICES didn't.

While being at it, do the same change for NFTNL_FLOWTABLE_DEVICES as
well to make code a bit more consistent although the problem was fixed
for flowtables with commit f8eed54150fd4 ("flowtable: Fix for reading
garbage") already (but in the other direction).

Fixes: e3ac19b5ec162 ("chain: multi-device support")
Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 src/chain.c     | 1 +
 src/flowtable.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/src/chain.c b/src/chain.c
index b4066e4d4e888..94a9e43a17548 100644
--- a/src/chain.c
+++ b/src/chain.c
@@ -364,6 +364,7 @@ const void *nftnl_chain_get_data(const struct nftnl_chain *c, uint16_t attr,
 		*data_len = strlen(c->dev) + 1;
 		return c->dev;
 	case NFTNL_CHAIN_DEVICES:
+		*data_len = 0;
 		return &c->dev_array[0];
 	}
 	return NULL;
diff --git a/src/flowtable.c b/src/flowtable.c
index 1e235d0ba50fa..635322d7fa563 100644
--- a/src/flowtable.c
+++ b/src/flowtable.c
@@ -230,6 +230,7 @@ const void *nftnl_flowtable_get_data(const struct nftnl_flowtable *c,
 		*data_len = sizeof(int32_t);
 		return &c->family;
 	case NFTNL_FLOWTABLE_DEVICES:
+		*data_len = 0;
 		return &c->dev_array[0];
 	case NFTNL_FLOWTABLE_SIZE:
 		*data_len = sizeof(int32_t);
-- 
2.24.1