On 2/23/24 06:36, Wen Gu wrote:
One solution to this issue I can think of is to check whether
filp->private_data has been changed when the sock_fasync holds the sock lock,
but it inevitably changes the general code..
diff --git a/net/socket.c b/net/socket.c
index ed3df2f749bf..a28435195854 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1443,6 +1443,11 @@ static int sock_fasync(int fd, struct file *filp, int on)
return -EINVAL;
lock_sock(sk);
+ /* filp->private_data has changed */
+ if (on && unlikely(sock != filp->private_data)) {
+ release_sock(sk);
+ return -EAGAIN;
+ }
fasync_helper(fd, filp, on, &wq->fasync_list);
if (!wq->fasync_list)
Let's see if anyone else has a better idea.
IIUC this is not a solution just because it decreases the probability of the race
but doesn't eliminate it completely - an underlying socket switch (e.g. changing
'filp->private_data') may happen when 'fasync_helper()' is in progress.
Dmitry
