[PATCH 4.14 169/229] tcp: fix over estimation in sk_forced_mem_schedule()

Greg Kroah-Hartman
2022-08-23T10:10:21Z

From: Eric Dumazet <edumazet@google.com>

commit c4ee118561a0f74442439b7b5b486db1ac1ddfeb upstream.

sk_forced_mem_schedule() has a bug similar to ones fixed
in commit 7c80b038d23e ("net: fix sk_wmem_schedule() and
sk_rmem_schedule() errors")

While this bug has little chance to trigger in old kernels,
we need to fix it before the following patch.

Fixes: d83769a580f1 ("tcp: fix possible deadlock in tcp_send_fin()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Wei Wang <weiwan@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/tcp_output.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3086,11 +3086,12 @@ void tcp_xmit_retransmit_queue(struct so
*/
void sk_forced_mem_schedule(struct sock *sk, int size)
{
- int amt;
+ int delta, amt;

- if (size <= sk->sk_forward_alloc)
+ delta = size - sk->sk_forward_alloc;
+ if (delta <= 0)
return;
- amt = sk_mem_pages(size);
+ amt = sk_mem_pages(delta);
sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
sk_memory_allocated_add(sk, amt);