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sctp: Allow blocking on I/O locks even with non-blocking sockets

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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
This commit is contained in:
Mark Johnston 2021-09-14 09:02:05 -04:00
parent fa0463c384
commit e6c19aa94d
1 changed files with 1 additions and 1 deletions
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2
sys/netinet/sctputil.c
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@ -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;
}