git: 32f1d05f783d - stable/13 - sctp: Allow blocking on I/O locks even with non-blocking sockets

[Mark Johnston]

The branch stable/13 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=32f1d05f783de24f97ec56aca454e52c7d1071bf

commit 32f1d05f783de24f97ec56aca454e52c7d1071bf
Author:     Mark Johnston <markj at FreeBSD.org>
AuthorDate: 2021-09-14 13:02:05 +0000
Commit:     Mark Johnston <markj at FreeBSD.org>
CommitDate: 2021-09-21 13:38:39 +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 at syzkaller.appspotmail.com
    Reviewed by:    tuexen
    Sponsored by:   The FreeBSD Foundation
    
    (cherry picked from commit e6c19aa94da4a799472f8b82f196ffc42d0dbdaf)
---
 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 ad4409f666df..b01ace4d1fb9 100644
--- a/sys/netinet/sctputil.c
+++ b/sys/netinet/sctputil.c
@@ -5586,7 +5586,7 @@ sctp_sorecvmsg(struct socket *so,
 		    rwnd_req, block_allowed, so->so_rcv.sb_cc, (uint32_t)uio->uio_resid);
 	}
 
-	error = sblock(&so->so_rcv, (block_allowed ? SBL_WAIT : 0));
+	error = sblock(&so->so_rcv, SBLOCKWAIT(in_flags));
 	if (error) {
 		goto release_unlocked;
 	}