From: Eric Dumazet edumazet@google.com
[ Upstream commit f8d9d938514f46c4892aff6bfe32f425e84d81cc ]
syzbot found that mixing sendpage() and sendmsg(MSG_ZEROCOPY) calls over the same TCP socket would again trigger the infamous warning in inet_sock_destruct()
WARN_ON(sk_forward_alloc_get(sk));
While Talal took into account a mix of regular copied data and MSG_ZEROCOPY one in the same skb, the sendpage() path has been forgotten.
We want the charging to happen for sendpage(), because pages could be coming from a pipe. What is missing is the downgrading of pure zerocopy status to make sure sk_forward_alloc will stay synced.
Add tcp_downgrade_zcopy_pure() helper so that we can use it from the two callers.
Fixes: 9b65b17db723 ("net: avoid double accounting for pure zerocopy skbs") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Cc: Talal Ahmad talalahmad@google.com Cc: Arjun Roy arjunroy@google.com Cc: Willem de Bruijn willemb@google.com Acked-by: Soheil Hassas Yeganeh soheil@google.com Link: https://lore.kernel.org/r/20220203225547.665114-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/tcp.c | 33 +++++++++++++++++++-------------- 1 file changed, 19 insertions(+), 14 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 94cbba9fb12b1..28abb0bb1c515 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -936,6 +936,22 @@ void tcp_remove_empty_skb(struct sock *sk) } }
+/* skb changing from pure zc to mixed, must charge zc */ +static int tcp_downgrade_zcopy_pure(struct sock *sk, struct sk_buff *skb) +{ + if (unlikely(skb_zcopy_pure(skb))) { + u32 extra = skb->truesize - + SKB_TRUESIZE(skb_end_offset(skb)); + + if (!sk_wmem_schedule(sk, extra)) + return -ENOMEM; + + sk_mem_charge(sk, extra); + skb_shinfo(skb)->flags &= ~SKBFL_PURE_ZEROCOPY; + } + return 0; +} + static struct sk_buff *tcp_build_frag(struct sock *sk, int size_goal, int flags, struct page *page, int offset, size_t *size) { @@ -971,7 +987,7 @@ static struct sk_buff *tcp_build_frag(struct sock *sk, int size_goal, int flags, tcp_mark_push(tp, skb); goto new_segment; } - if (!sk_wmem_schedule(sk, copy)) + if (tcp_downgrade_zcopy_pure(sk, skb) || !sk_wmem_schedule(sk, copy)) return NULL;
if (can_coalesce) { @@ -1319,19 +1335,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
copy = min_t(int, copy, pfrag->size - pfrag->offset);
- /* skb changing from pure zc to mixed, must charge zc */ - if (unlikely(skb_zcopy_pure(skb))) { - u32 extra = skb->truesize - - SKB_TRUESIZE(skb_end_offset(skb)); - - if (!sk_wmem_schedule(sk, extra)) - goto wait_for_space; - - sk_mem_charge(sk, extra); - skb_shinfo(skb)->flags &= ~SKBFL_PURE_ZEROCOPY; - } - - if (!sk_wmem_schedule(sk, copy)) + if (tcp_downgrade_zcopy_pure(sk, skb) || + !sk_wmem_schedule(sk, copy)) goto wait_for_space;
err = skb_copy_to_page_nocache(sk, &msg->msg_iter, skb,