From: Daniel P. Berrangé <berrange@redhat.com> A recent commit caused the virFDStreamRead method to loop reading data until the provided buffer is full. Unfortunately the EOF handling was not quiet correct. * When seeing a virFDStreamMsg with length zero, it would still loop trying to read more and then get an error that the thread has quit. * When seeing a virFDStreamMsg with length zero on subsequent iterations, it would discard this message, which would in turn prevent the caller from ever seeing the 'ret == 0' return value indicating EOF. The caller would then try to read again and get an error about the stream being closed. Fixes: e23fd0b7fd36c41e6db49df4f4962762d3ef6ab0 Reported-by: Roman Bogorodskiy <bogorodskiy@gmail.com> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> --- src/util/virfdstream.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/src/util/virfdstream.c b/src/util/virfdstream.c index cd2ede4501..9fe70be0b9 100644 --- a/src/util/virfdstream.c +++ b/src/util/virfdstream.c @@ -907,6 +907,7 @@ static int virFDStreamRead(virStreamPtr st, char *bytes, size_t nbytes) virFDStreamMsg *msg = NULL; size_t got = 0; size_t bsz = 0; + bool isEOF; more: while (!(msg = fdst->msg)) { @@ -945,6 +946,7 @@ static int virFDStreamRead(virStreamPtr st, char *bytes, size_t nbytes) goto cleanup; } + isEOF = msg->stream.data.len == 0; bsz = msg->stream.data.len - msg->stream.data.offset; if (nbytes < bsz) bsz = nbytes; @@ -956,12 +958,24 @@ static int virFDStreamRead(virStreamPtr st, char *bytes, size_t nbytes) nbytes -= bsz; msg->stream.data.offset += bsz; - if (msg->stream.data.offset == msg->stream.data.len) { + /* If we stream msg is fully consumed, then remove + * it from the queue. + * + * Exception: if this is the second time around the + * loop, and the msg indicated an EOF, we must leave + * it on the queue so a subsequent read sees the + * ret == 0 EOF condition + */ + if (msg->stream.data.offset == msg->stream.data.len && + (!isEOF || got == 0)) { virFDStreamMsgQueuePop(fdst, fdst->fd, "pipe"); virFDStreamMsgFree(msg); } - if (nbytes > 0) { + /* If we didn't just see EOF and can read more into + * 'bytes' then retry the loop + */ + if (nbytes > 0 && !isEOF) { goto more; } ret = got; -- 2.53.0