[Qemu-devel] [PATCH v2] qemu-sockets: Report explicit error if unlink fails

[Cole Robinson <crobinso@redhat.com>]

Consider this case:

$ ls -ld ~/root-owned/
drwx--x--x. 2 root root 4096 Apr 29 12:55 /home/crobinso/root-owned/
$ ls -l ~/root-owned/foo.sock
-rwxrwxrwx. 1 crobinso crobinso 0 Apr 29 12:55 /home/crobinso/root-owned/foo.sock

$ qemu-system-x86_64 -vnc unix:~/root-owned/foo.sock
qemu-system-x86_64: -vnc unix:/home/crobinso/root-owned/foo.sock: Failed to start VNC server: Failed to bind socket to /home/crobinso/root-owned/foo.sock: Address already in use

...which is techinically true, but the real error is that we failed to
unlink. So report it.

This may seem pathological but it's a real possibility via libvirt.

Signed-off-by: Cole Robinson <crobinso@redhat.com>
---
Sigh, sent an old version of the patch accidentally

v2:
    Fix the access check
    Better commit message

 util/qemu-sockets.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
index 87c9bc6..527f488 100644
--- a/util/qemu-sockets.c
+++ b/util/qemu-sockets.c
@@ -729,7 +729,11 @@ int unix_listen_opts(QemuOpts *opts, Error **errp)
         qemu_opt_set(opts, "path", un.sun_path, &error_abort);
     }
 
-    unlink(un.sun_path);
+    if ((access(un.sun_path, F_OK) == 0) &&
+        unlink(un.sun_path) < 0) {
+        error_setg_errno(errp, errno, "Failed to unlink socket %s", un.sun_path);
+        goto err;
+    }
     if (bind(sock, (struct sockaddr*) &un, sizeof(un)) < 0) {
         error_setg_errno(errp, errno, "Failed to bind socket to %s", un.sun_path);
         goto err;
-- 
2.3.6