sk_buff: avoid potentially clearing 'slow_gro' field

If skb_dst_set_noref() is invoked with a NULL dst, the 'slow_gro'
field is cleared, too. That could lead to wrong behavior if
the skb later enters the GRO stage.

Fix the potential issue replacing preserving a non-zero value of
the 'slow_gro' field.

Additionally, fix a comment typo.

Reported-by: Sabrina Dubroca <sd@queasysnail.net>
Reported-by: Jakub Kicinski <kuba@kernel.org>
Fixes: 8a886b142bd0 ("sk_buff: track dst status in slow_gro")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/aa42529252dc8bb02bd42e8629427040d1058537.1627662501.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index b1e5bbf..2bcdc8c 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1009,7 +1009,7 @@ static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)
 static inline void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst)
 {
        WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
-       skb->slow_gro = !!dst;
+       skb->slow_gro |= !!dst;
        skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF;
 }
 

diff --git a/net/core/dev.c b/net/core/dev.c
index b51e41d..64e1a5f 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6022,7 +6022,7 @@ static void gro_list_prepare(const struct list_head *head,
                                       skb_mac_header(skb),
                                       maclen);
 
-               /* in most common scenarions _state is 0
+               /* in most common scenarions 'slow_gro' is 0
                 * otherwise we are already on some slower paths
                 * either skip all the infrequent tests altogether or
                 * avoid trying too hard to skip each of them individually