virtio-9p: Implement Security model for mknod

Mapped mode stores extended attributes in the user space of the extended
attributes. Given that the user space extended attributes are available
to regular files only, special files are created as regular files on the
fileserver and appropriate mode bits are added to the extended attributes.
This method presents all special files and symlinks as regular files on the
fileserver while they are represented as special files on the guest mount.

On Host/Fileserver:
-rw-------. 1 virfsuid virtfsgid 0 2010-05-11 09:36 afifo
-rw-------. 1 virfsuid virtfsgid 0 2010-05-11 09:32 blkdev
-rw-------. 1 virfsuid virtfsgid 0 2010-05-11 09:33 chardev

On Guest/Client:
prw-r--r-- 1 guestuser guestuser 0 2010-05-11 12:36 afifo
brw-r--r-- 1 guestuser guestuser 0, 0 2010-05-11 12:32 blkdev
crw-r--r-- 1 guestuser guestuser 4, 5 2010-05-11 12:33 chardev

In the passthrough securit model, specifal files are directly created
on the fileserver. But the user credential

Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

hw/file-op-9p.h

@@ -51,7 +51,7 @@ typedef struct FileOperations
     ssize_t (*readlink)(FsContext *, const char *, char *, size_t);
     int (*chmod)(FsContext *, const char *, FsCred *);
     int (*chown)(FsContext *, const char *, FsCred *);
-    int (*mknod)(FsContext *, const char *, mode_t, dev_t);
+    int (*mknod)(FsContext *, const char *, FsCred *);
     int (*mksock)(FsContext *, const char *);
     int (*utime)(FsContext *, const char *, const struct utimbuf *);
     int (*remove)(FsContext *, const char *);

hw/virtio-9p-local.c

@@ -195,9 +195,39 @@ static int local_chmod(FsContext *fs_ctx, const char *path, FsCred *credp)
     return -1;
 }
 
-static int local_mknod(FsContext *ctx, const char *path, mode_t mode, dev_t dev)
+static int local_mknod(FsContext *fs_ctx, const char *path, FsCred *credp)
 {
-    return mknod(rpath(ctx, path), mode, dev);
+    int err = -1;
+    int serrno = 0;
+
+    /* Determine the security model */
+    if (fs_ctx->fs_sm == SM_MAPPED) {
+        err = mknod(rpath(fs_ctx, path), SM_LOCAL_MODE_BITS|S_IFREG, 0);
+        if (err == -1) {
+            return err;
+        }
+        local_set_xattr(rpath(fs_ctx, path), credp);
+        if (err == -1) {
+            serrno = errno;
+            goto err_end;
+        }
+    } else if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        err = mknod(rpath(fs_ctx, path), credp->fc_mode, credp->fc_rdev);
+        if (err == -1) {
+            return err;
+        }
+        err = local_post_create_passthrough(fs_ctx, path, credp);
+        if (err == -1) {
+            serrno = errno;
+            goto err_end;
+        }
+    }
+    return err;
+
+err_end:
+    remove(rpath(fs_ctx, path));
+    errno = serrno;
+    return err;
 }
 
 static int local_mksock(FsContext *ctx2, const char *path)

hw/virtio-9p.c

@@ -160,9 +160,15 @@ static int v9fs_do_chmod(V9fsState *s, V9fsString *path, mode_t mode)
     return s->ops->chmod(&s->ctx, path->data, &cred);
 }
 
-static int v9fs_do_mknod(V9fsState *s, V9fsString *path, mode_t mode, dev_t dev)
+static int v9fs_do_mknod(V9fsState *s, V9fsCreateState *vs, mode_t mode,
+        dev_t dev)
 {
-    return s->ops->mknod(&s->ctx, path->data, mode, dev);
+    FsCred cred;
+    cred_init(&cred);
+    cred.fc_uid = vs->fidp->uid;
+    cred.fc_mode = mode;
+    cred.fc_rdev = dev;
+    return s->ops->mknod(&s->ctx, vs->fullname.data, &cred);
 }
 
 static int v9fs_do_mksock(V9fsState *s, V9fsString *path)
@@ -1825,10 +1831,10 @@ static void v9fs_create_post_lstat(V9fsState *s, V9fsCreateState *vs, int err)
         }
 
         nmode |= vs->perm & 0777;
-        err = v9fs_do_mknod(s, &vs->fullname, nmode, makedev(major, minor));
+        err = v9fs_do_mknod(s, vs, nmode, makedev(major, minor));
         v9fs_create_post_perms(s, vs, err);
     } else if (vs->perm & P9_STAT_MODE_NAMED_PIPE) {
-        err = v9fs_do_mknod(s, &vs->fullname, S_IFIFO | (vs->mode & 0777), 0);
+        err = v9fs_do_mknod(s, vs, S_IFIFO | (vs->perm & 0777), 0);
         v9fs_post_create(s, vs, err);
     } else if (vs->perm & P9_STAT_MODE_SOCKET) {
         err = v9fs_do_mksock(s, &vs->fullname);