[PATCH] nft: nft_set_attr_get_u32 null pointer deref

[Phil Oester <kernel@xxxxxxxxxxxx>]

As reported by John Sager, nft_set_attr_get_u32 can cause a segfault because
nft_set_attr_get can return NULL.  Check for a non-NULL pointer before
dereferencing.

This closes netfilter bugzilla #868.

Signed-off-by: Phil Oester <kernel@xxxxxxxxxxxx>

diff --git a/src/set.c b/src/set.c
index 74ec1e3..85f73cf 100644
--- a/src/set.c
+++ b/src/set.c
@@ -183,8 +183,8 @@ EXPORT_SYMBOL(nft_set_attr_get_str);
 
 uint32_t nft_set_attr_get_u32(struct nft_set *s, uint16_t attr)
 {
-	uint32_t val = *((uint32_t *)nft_set_attr_get(s, attr));
-	return val;
+	const void *val = nft_set_attr_get(s, attr);
+	return val ? *(uint32_t *)val : 0;
 }
 EXPORT_SYMBOL(nft_set_attr_get_u32);