From: Karsten Graul <kgraul@xxxxxxxxxxxxx>
Date: Tue, 16 Oct 2018 16:45:54 +0200
> Commit dd979b4df817 ("net: simplify sock_poll_wait") breaks tcp_poll for
> SMC fallback: An AF_SMC socket establishes an internal TCP socket for the
> CLC handshake with the remote peer. Whenever the SMC connection can not be
> established this CLC socket is used as a fallback. All socket operations on the
> SMC socket are then forwarded to the CLC socket. In case of poll, the
> file->private_data pointer references the SMC socket because the CLC socket has
> no file assigned. This causes tcp_poll to wait on the wrong socket.
>
> This patch fixes the issue by (re)introducing a sock_poll_wait variant with
> a socket parameter, and let tcp_poll use this variant.
>
> Fixes: dd979b4df817 ("net: simplify sock_poll_wait")
> Signed-off-by: Karsten Graul <kgraul@xxxxxxxxxxxxx>
Generally speaking, if the invariant of filp->private_data == sock
does not actually hold true universally, I'd rather revert the
simplifications and add a big comment to sock_poll_wait() explaining
this.
Thank you.
