| Message ID | 20180131042147.GA13245@embeddedgus |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | tcp_nv: fix potential integer overflow in tcpnv_acked | expand |
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> Date: Tue, 30 Jan 2018 22:21:48 -0600 > 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> Applied.
diff --git a/net/ipv4/tcp_nv.c b/net/ipv4/tcp_nv.c index ddbce73..764298e 100644 --- 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
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> --- net/ipv4/tcp_nv.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)