net: fix possible overflow in __sk_mem_raise_allocated()

mainline inclusion
from mainline-v5.0
commit 5bf325a53202
category: bugfix
bugzilla: 9551
CVE: NA

-------------------------------------------------

With many active TCP sockets, fat TCP sockets could fool
__sk_mem_raise_allocated() thanks to an overflow.

They would increase their share of the memory, instead
of decreasing it.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NShangli <shangli1@huawei.com>
Reviewed-by: NMao Wenan <maowenan@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

include/net/sock.h

@@ -1266,7 +1266,7 @@ static inline void sk_sockets_allocated_inc(struct sock *sk)
 	percpu_counter_inc(sk->sk_prot->sockets_allocated);
 }
 
-static inline int
+static inline u64
 sk_sockets_allocated_read_positive(struct sock *sk)
 {
 	return percpu_counter_read_positive(sk->sk_prot->sockets_allocated);

net/core/sock.c

@@ -2433,7 +2433,7 @@ int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind)
 	}
 
 	if (sk_has_memory_pressure(sk)) {
-		int alloc;
+		u64 alloc;
 
 		if (!sk_under_memory_pressure(sk))
 			return 1;