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tcp: take care of mixed splice()/sendmsg(MSG_ZEROCOPY) case 

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: 9b65b17db7 ("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>
This commit is contained in:
Eric Dumazet 2022-02-03 14:55:47 -08:00 committed by Jakub Kicinski
parent 40106e005b
commit f8d9d93851
1 changed files with 19 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
net/ipv4/tcp.c
View File

@ -937,6 +937,22 @@ 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)
{
@ -972,7 +988,7 @@ new_segment:
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) {
@ -1320,19 +1336,8 @@ new_segment:
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,