From: Willem de Bruijn willemb@google.com
[ Upstream commit 185ce5c38ea76f29b6bd9c7c8c7a5e5408834920 ]
Zerocopy skbs without completion notification were added for packet sockets with PACKET_TX_RING user buffers. Those signal completion through the TP_STATUS_USER bit in the ring. Zerocopy annotation was added only to avoid premature notification after clone or orphan, by triggering a copy on these paths for these packets.
The mechanism had to define a special "no-uarg" mode because packet sockets already use skb_uarg(skb) == skb_shinfo(skb)->destructor_arg for a different pointer.
Before deferencing skb_uarg(skb), verify that it is a real pointer.
Fixes: 5cd8d46ea1562 ("packet: copy user buffers before orphan or clone") Signed-off-by: Willem de Bruijn willemb@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/skbuff.h | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1333,10 +1333,12 @@ static inline void skb_zcopy_clear(struc struct ubuf_info *uarg = skb_zcopy(skb);
if (uarg) { - if (uarg->callback == sock_zerocopy_callback) { + if (skb_zcopy_is_nouarg(skb)) { + /* no notification callback */ + } else if (uarg->callback == sock_zerocopy_callback) { uarg->zerocopy = uarg->zerocopy && zerocopy; sock_zerocopy_put(uarg); - } else if (!skb_zcopy_is_nouarg(skb)) { + } else { uarg->callback(uarg, zerocopy); }
@@ -2587,7 +2589,8 @@ static inline int skb_orphan_frags(struc { if (likely(!skb_zcopy(skb))) return 0; - if (skb_uarg(skb)->callback == sock_zerocopy_callback) + if (!skb_zcopy_is_nouarg(skb) && + skb_uarg(skb)->callback == sock_zerocopy_callback) return 0; return skb_copy_ubufs(skb, gfp_mask); }