tcp_nv: fix potential integer overflow in tcpnv_acked

BugLink: http://bugs.launchpad.net/bugs/1774063
[ Upstream commit e4823fbd229bfbba368b40cdadb8f4eeb20604cc ]

Add suffix ULL to constant 80000 in order to avoid a potential integer
overflow and give the compiler complete information about the proper
arithmetic to use. Notice that this constant is used in a context that
expects an expression of type u64.

The current cast to u64 effectively applies to the whole expression
as an argument of type u64 to be passed to div64_u64, but it does
not prevent it from being evaluated using 32-bit arithmetic instead
of 64-bit arithmetic.

Also, once the expression is properly evaluated using 64-bit arithmentic,
there is no need for the parentheses and the external cast to u64.

Addresses-Coverity-ID: 1357588 ("Unintentional integer overflow")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/net/ipv4/tcp_nv.c b/net/ipv4/tcp_nv.c
index 0b5a05bd82e35895f1b69b255a6ae2fd0ac86b47..d18f4672beaec8de511b0a2db745d1398ccce601 100644 (file)
--- a/net/ipv4/tcp_nv.c
+++ b/net/ipv4/tcp_nv.c
@@ -364,7 +364,7 @@ static void tcpnv_acked(struct sock *sk, const struct ack_sample *sample)
                 */
                cwnd_by_slope = (u32)
                        div64_u64(((u64)ca->nv_rtt_max_rate) * ca->nv_min_rtt,
-                                 (u64)(80000 * tp->mss_cache));
+                                 80000ULL * tp->mss_cache);
                max_win = cwnd_by_slope + nv_pad;
 
                /* If cwnd > max_win, decrease cwnd