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authorArnd Bergmann <arnd@arndb.de>2017-07-28 16:41:37 +0200
committerDavid S. Miller <davem@davemloft.net>2017-07-29 23:26:29 -0700
commitefe967cdec32af93e15839cc639695ec5f637771 (patch)
treebde5ac076216fb99c01bd39e94f8cd985b793534 /net
parent4084e01db9d52213bd2d63941c72d2788b38e1ed (diff)
downloadlinux-efe967cdec32af93e15839cc639695ec5f637771.tar.bz2
tcp: avoid bogus gcc-7 array-bounds warning
When using CONFIG_UBSAN_SANITIZE_ALL, the TCP code produces a false-positive warning: net/ipv4/tcp_output.c: In function 'tcp_connect': net/ipv4/tcp_output.c:2207:40: error: array subscript is below array bounds [-Werror=array-bounds] tp->chrono_stat[tp->chrono_type - 1] += now - tp->chrono_start; ^~ net/ipv4/tcp_output.c:2207:40: error: array subscript is below array bounds [-Werror=array-bounds] tp->chrono_stat[tp->chrono_type - 1] += now - tp->chrono_start; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~ I have opened a gcc bug for this, but distros have already shipped compilers with this problem, and it's not clear yet whether there is a way for gcc to avoid the warning. As the problem is related to the bitfield access, this introduces a temporary variable to store the old enum value. I did not notice this warning earlier, since UBSAN is disabled when building with COMPILE_TEST, and that was always turned on in both allmodconfig and randconfig tests. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81601 Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp_output.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 4e985dea1dd2..2f1588bf73da 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2202,9 +2202,10 @@ static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
{
const u32 now = tcp_jiffies32;
+ enum tcp_chrono old = tp->chrono_type;
- if (tp->chrono_type > TCP_CHRONO_UNSPEC)
- tp->chrono_stat[tp->chrono_type - 1] += now - tp->chrono_start;
+ if (old > TCP_CHRONO_UNSPEC)
+ tp->chrono_stat[old - 1] += now - tp->chrono_start;
tp->chrono_start = now;
tp->chrono_type = new;
}