net: always initialize pagedlen

[ Upstream commit aba36930a35e7f1fe1319b203f25c05d6c119936 ]

In ip packet generation, pagedlen is initialized for each skb at the
start of the loop in __ip(6)_append_data, before label alloc_new_skb.

Depending on compiler options, code can be generated that jumps to
this label, triggering use of an an uninitialized variable.

In practice, at -O2, the generated code moves the initialization below
the label. But the code should not rely on that for correctness.

Fixes: 15e36f5b8e98 ("udp: paged allocation with gso")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index d630918..fbf3012 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -940,7 +940,7 @@ static int __ip_append_data(struct sock *sk,
                        unsigned int fraglen;
                        unsigned int fraggap;
                        unsigned int alloclen;
-                       unsigned int pagedlen = 0;
+                       unsigned int pagedlen;
                        struct sk_buff *skb_prev;
 alloc_new_skb:
                        skb_prev = skb;
@@ -957,6 +957,7 @@ alloc_new_skb:
                        if (datalen > mtu - fragheaderlen)
                                datalen = maxfraglen - fragheaderlen;
                        fraglen = datalen + fragheaderlen;
+                       pagedlen = 0;
 
                        if ((flags & MSG_MORE) &&
                            !(rt->dst.dev->features&NETIF_F_SG))

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index eed9231..9886a84 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1357,7 +1357,7 @@ emsgsize:
                        unsigned int fraglen;
                        unsigned int fraggap;
                        unsigned int alloclen;
-                       unsigned int pagedlen = 0;
+                       unsigned int pagedlen;
 alloc_new_skb:
                        /* There's no room in the current skb */
                        if (skb)
@@ -1381,6 +1381,7 @@ alloc_new_skb:
                        if (datalen > (cork->length <= mtu && !(cork->flags & IPCORK_ALLFRAG) ? mtu : maxfraglen) - fragheaderlen)
                                datalen = maxfraglen - fragheaderlen - rt->dst.trailer_len;
                        fraglen = datalen + fragheaderlen;
+                       pagedlen = 0;
 
                        if ((flags & MSG_MORE) &&
                            !(rt->dst.dev->features&NETIF_F_SG))