[Libguestfs] [nbdkit PATCH 1/2] connections: Report mid-message EOF as fatal
If we encounter any read error in the middle of the message
(including the NBD_CMD_WRITE payload), we are no longer in sync
with the client and should not try to read anything further.
For mid-message EOF, the problem wasn't too bad (the next
iteration of the loop would also see EOF); but if it is some
other error (perhaps a transient EIO due to reading from a
flaky block device), not marking the connection failed could
result in us trying to treat the tail of the previous partial
payload as further commands. Usually a magic number mismatch
would flag the problem, but we should never base our behavior
on the contents of that random payload.
Signed-off-by: Eric Blake <eblake(a)redhat.com>
---
src/connections.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)
diff --git a/src/connections.c b/src/connections.c
index 0cbf54a..d0ef6a5 100644
--- a/src/connections.c
+++ b/src/connections.c
@@ -873,7 +873,7 @@ handle_request (struct connection *conn,
return r;
}
-static void
+static int
skip_over_write_buffer (int sock, size_t count)
{
char buf[BUFSIZ];
@@ -883,12 +883,16 @@ skip_over_write_buffer (int sock, size_t count)
r = read (sock, buf, count > BUFSIZ ? BUFSIZ : count);
if (r == -1) {
nbdkit_error ("skipping write buffer: %m");
- return;
+ return -1;
+ }
+ if (r == 0) {
+ nbdkit_error ("unexpected early EOF");
+ errno = EBADMSG;
+ return -1;
}
- if (r == 0)
- return;
count -= r;
}
+ return 0;
}
/* Convert a system errno to an NBD_E* error code. */
@@ -965,8 +969,9 @@ recv_request_send_reply (struct connection *conn)
if (r == -1)
return -1;
if (r == 0) { /* request not valid */
- if (cmd == NBD_CMD_WRITE)
- skip_over_write_buffer (conn->sockin, count);
+ if (cmd == NBD_CMD_WRITE &&
+ skip_over_write_buffer (conn->sockin, count) < 0)
+ return -1;
goto send_reply;
}
@@ -976,8 +981,9 @@ recv_request_send_reply (struct connection *conn)
if (buf == NULL) {
perror ("malloc");
error = ENOMEM;
- if (cmd == NBD_CMD_WRITE)
- skip_over_write_buffer (conn->sockin, count);
+ if (cmd == NBD_CMD_WRITE &&
+ skip_over_write_buffer (conn->sockin, count) < 0)
+ return -1;
goto send_reply;
}
}
@@ -985,14 +991,14 @@ recv_request_send_reply (struct connection *conn)
/* Receive the write data buffer. */
if (cmd == NBD_CMD_WRITE) {
r = conn->recv (conn, buf, count);
+ if (r == 0) {
+ errno = EBADMSG;
+ r = -1;
+ }
if (r == -1) {
nbdkit_error ("read data: %m");
return -1;
}
- if (r == 0) {
- debug ("client closed input unexpectedly, closing connection");
- return 0; /* disconnect */
- }
}
/* Perform the request. Only this part happens inside the request lock. */
--
2.13.6