From 6b61ba29c78e26109426429c6d6b354f6e4443cd Mon Sep 17 00:00:00 2001 From: David Mirabito via Linuxptp-devel Date: Tue, 19 Mar 2019 13:42:48 +1100 Subject: [PATCH] Avoid fault when receiving zero length packets The manpage for recvmsg says -1 will be returned on error, Zero indicates an "orderly shutdown", presumably only in case of stream sockets. Further, UNIX Network Programming, Vol 1 says ".. a return value of 0 from recvfrom is acceptable for a datagram protocol" Such packets have been observed in the wild, aimed at PTP's multicast address and port, possibly related to malformed management queries. Patch to properly check return from recvmesg and not trigger the fault codepath. Instead, such packets are treated as "Bad Message" the same as non-zero but still too-short UDP payloads. Signed-off-by: David Mirabito --- port.c | 2 +- sk.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/port.c b/port.c index ad9554f..9264211 100644 --- a/port.c +++ b/port.c @@ -2563,7 +2563,7 @@ static enum fsm_event bc_event(struct port *p, int fd_index) msg->hwts.type = p->timestamping; cnt = transport_recv(p->trp, fd, msg); - if (cnt <= 0) { + if (cnt < 0) { pr_err("port %hu: recv message failed", portnum(p)); msg_put(msg); return EV_FAULT_DETECTED; diff --git a/sk.c b/sk.c index 30162eb..93ba77a 100644 --- a/sk.c +++ b/sk.c @@ -359,7 +359,7 @@ int sk_receive(int fd, void *buf, int buflen, } cnt = recvmsg(fd, &msg, flags); - if (cnt < 1) + if (cnt < 0) pr_err("recvmsg%sfailed: %m", flags == MSG_ERRQUEUE ? " tx timestamp " : " ");