From: Willem de Bruijn willemb@google.com
[ 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 --- net/ipv4/ip_output.c | 3 ++- net/ipv6/ip6_output.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index d63091812342f..fbf30122e8bf2 100644 --- 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 eed9231c90ad5..9886a84c25117 100644 --- 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))