sctp: Allow blocking on I/O locks even with non-blocking sockets
There are two flags to request a non-blocking receive on a socket: MSG_NBIO and MSG_DONTWAIT. They are handled a bit differently in that soreceive_generic() and soreceive_stream() will block on the socket I/O lock when MSG_NBIO is set, but not if MSG_DONTWAIT is set. In general, MSG_NBIO seems to mean, "don't block if there is no data to receive" and MSG_DONTWAIT means "don't go to sleep for any reason". SCTP's soreceive implementation did not allow blocking on the I/O lock if either flag is set, but this violates an assumption in aio_process_sb(), which specifies MSG_NBIO but nonetheless expects to make progress if data is available to read. Change sctp_sorecvmsg() to block on the I/O lock only if MSG_DONTWAIT is not set. Reported by: syzbot+c7d22dbbb9aef509421d@syzkaller.appspotmail.com Reviewed by: tuexen MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D31915
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@ -5585,7 +5585,7 @@ sctp_sorecvmsg(struct socket *so,
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rwnd_req, block_allowed, so->so_rcv.sb_cc, (uint32_t)uio->uio_resid);
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}
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error = SOCK_IO_RECV_LOCK(so, (block_allowed ? SBL_WAIT : 0));
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error = SOCK_IO_RECV_LOCK(so, SBLOCKWAIT(in_flags));
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if (error) {
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goto release_unlocked;
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}
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