rds: annotate data-race around rs_seen_congestion

rs_seen_congestion is read in rds_poll() and written in rds_sendmsg()
and rds_poll() without any lock.  Use READ_ONCE()/WRITE_ONCE() to
annotate these lockless accesses and silence KCSAN.

Reported-by: syzbot+fbf3648ae7f5bdb05c59@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/6a0f8d94.050a0220.6b33c.0000.GAE@google.com/
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Reviewed-by: Allison Henderson <achender@kernel.org> 
Tested-by: Allison Henderson <achender@kernel.org>
Link: https://patch.msgid.link/20260522011621.304470-1-jiayuan.chen@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/rds/af_rds.c b/net/rds/af_rds.c
index 76f625986a7f24aadf2cf6da529a5370feadb1d2..93b2da63ed42ec1b669cd11532e455f6777d347b 100644 (file)
--- a/net/rds/af_rds.c
+++ b/net/rds/af_rds.c
@@ -219,7 +219,7 @@ static __poll_t rds_poll(struct file *file, struct socket *sock,
 
        poll_wait(file, sk_sleep(sk), wait);
 
-       if (rs->rs_seen_congestion)
+       if (READ_ONCE(rs->rs_seen_congestion))
                poll_wait(file, &rds_poll_waitq, wait);
 
        read_lock_irqsave(&rs->rs_recv_lock, flags);
@@ -247,7 +247,7 @@ static __poll_t rds_poll(struct file *file, struct socket *sock,
 
        /* clear state any time we wake a seen-congested socket */
        if (mask)
-               rs->rs_seen_congestion = 0;
+               WRITE_ONCE(rs->rs_seen_congestion, 0);
 
        return mask;
 }

diff --git a/net/rds/send.c b/net/rds/send.c
index d8b14ff9d366be4715a960a27d15256288434a7d..e5d58c29aabea3d434ff12d617fcdd642140bd2e 100644 (file)
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -1388,7 +1388,7 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
 
        ret = rds_cong_wait(conn->c_fcong, dport, nonblock, rs);
        if (ret) {
-               rs->rs_seen_congestion = 1;
+               WRITE_ONCE(rs->rs_seen_congestion, 1);
                goto out;
        }
        while (!rds_send_queue_rm(rs, conn, cpath, rm, rs->rs_bound_port,