Date: Tue, 14 Sep 2021 13:10:42 GMT From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: e6c19aa94da4 - main - sctp: Allow blocking on I/O locks even with non-blocking sockets Message-ID: <202109141310.18EDAg4K039603@gitrepo.freebsd.org>
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The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=e6c19aa94da4a799472f8b82f196ffc42d0dbdaf commit e6c19aa94da4a799472f8b82f196ffc42d0dbdaf Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2021-09-14 13:02:05 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2021-09-14 13:02:05 +0000 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 --- sys/netinet/sctputil.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/sys/netinet/sctputil.c b/sys/netinet/sctputil.c index 09d486038b65..c6cdd3315704 100644 --- a/sys/netinet/sctputil.c +++ b/sys/netinet/sctputil.c @@ -5585,7 +5585,7 @@ sctp_sorecvmsg(struct socket *so, rwnd_req, block_allowed, so->so_rcv.sb_cc, (uint32_t)uio->uio_resid); } - error = SOCK_IO_RECV_LOCK(so, (block_allowed ? SBL_WAIT : 0)); + error = SOCK_IO_RECV_LOCK(so, SBLOCKWAIT(in_flags)); if (error) { goto release_unlocked; }
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