From: Eric Dumazet edumazet@google.com
[ Upstream commit 8c70521238b7863c2af607e20bcba20f974c969b ]
challenge_timestamp can be read an written by concurrent threads.
This was expected, but we need to annotate the race to avoid potential issues.
Following patch moves challenge_timestamp and challenge_count to per-netns storage to provide better isolation.
Fixes: 354e4aa391ed ("tcp: RFC 5961 5.2 Blind Data Injection Attack Mitigation") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Eric Dumazet edumazet@google.com Acked-by: Neal Cardwell ncardwell@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/tcp_input.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index b1637990d5708..e5435156e545d 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3630,11 +3630,11 @@ static void tcp_send_challenge_ack(struct sock *sk)
/* Then check host-wide RFC 5961 rate limit. */ now = jiffies / HZ; - if (now != challenge_timestamp) { + if (now != READ_ONCE(challenge_timestamp)) { u32 ack_limit = READ_ONCE(net->ipv4.sysctl_tcp_challenge_ack_limit); u32 half = (ack_limit + 1) >> 1;
- challenge_timestamp = now; + WRITE_ONCE(challenge_timestamp, now); WRITE_ONCE(challenge_count, half + prandom_u32_max(ack_limit)); } count = READ_ONCE(challenge_count);