Patchwork [V7,7/9] virtio-9p: Support for creating special files

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Submitter Mohan Kumar M
Date March 4, 2011, 9:25 a.m.
Message ID <1299230756-1644-8-git-send-email-mohan@in.ibm.com>
Download mbox | patch
Permalink /patch/85388/
State New
Headers show

Comments

Mohan Kumar M - March 4, 2011, 9:25 a.m.
Add both chroot worker and qemu side interfaces to create special files
(directory, device nodes, links and symbolic links)

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
---
 hw/9pfs/virtio-9p-chroot-worker.c |   52 ++++++++++++++++++++
 hw/9pfs/virtio-9p-chroot.c        |   23 +++++++++
 hw/9pfs/virtio-9p-chroot.h        |    1 +
 hw/9pfs/virtio-9p-local.c         |   97 +++++++++++++++++++++++++------------
 4 files changed, 142 insertions(+), 31 deletions(-)
Stefan Hajnoczi - March 4, 2011, 11:06 a.m.
On Fri, Mar 4, 2011 at 9:25 AM, M. Mohan Kumar <mohan@in.ibm.com> wrote:
> +static int chroot_do_create_special(V9fsFileObjectRequest *request)
> +{
> +    int cur_uid, cur_gid;
> +    int retval = -1;
> +
> +    cur_uid = geteuid();
> +    cur_gid = getegid();
> +
> +    if (setfsuid(request->data.uid) < 0) {
> +        return -errno;
> +    }
> +    if (setfsgid(request->data.gid) < 0) {
> +        retval = -errno;
> +        goto unset_uid;
> +    }
> +
> +    switch (request->data.type) {
> +    case T_MKDIR:
> +        retval = mkdir(request->path.path, request->data.mode);
> +        break;
> +    case T_SYMLINK:
> +        retval = symlink(request->path.old_path, request->path.path);
> +        break;
> +    case T_LINK:
> +        retval = link(request->path.old_path, request->path.path);
> +        break;
> +    default:
> +        retval = mknod(request->path.path, request->data.mode,
> +                        request->data.dev);
> +        break;
> +    }
> +
> +    if (retval < 0) {
> +        retval = -errno;
> +    }
> +    setfsgid(cur_gid);
> +unset_uid:
> +    setfsuid(cur_uid);
> +    return retval;
> +}

It would be nice to take this one step further and move file create
and open here too.  The prototype we need is:

static int chroot_handle_request(V9fsFileObjectRequest *request, int *fd)
{
    *fd = -1;

It returns 0 on success or -errno and *fd >= 0 if a file descriptor
was opened and -1 otherwise.

This function becomes the main request processing function called from
v9fs_chroot() and the switch statement there can be eliminated.

Sending the response back to QEMU then gets a cleaned up prototype:
chroot_sendfd(int chroot_sock, int result, int fd) where result is 0
on success or -errno and fd >= 0 if present or -1 if not.

> +int v9fs_create_special(FsContext *fs_ctx, V9fsFileObjectRequest *request)
> +{
> +    int retval, sock_error;
> +    qemu_mutex_lock(&fs_ctx->chroot_mutex);
> +    if (fs_ctx->chroot_ioerror) {
> +        retval = -EIO;
> +        goto unlock;
> +    }
> +    if (v9fs_write_request(fs_ctx->chroot_socket, request) < 0) {
> +        fs_ctx->chroot_ioerror = 1;
> +        retval = -EIO;
> +        goto unlock;
> +    }
> +    retval = v9fs_receivefd(fs_ctx->chroot_socket, &sock_error);
> +    if (retval < 0 && sock_error) {
> +        fs_ctx->chroot_ioerror = 1;
> +    }
> +unlock:
> +    qemu_mutex_unlock(&fs_ctx->chroot_mutex);
> +    return retval;
> +}

This function is a duplicate of v9fs_request().  Can't there be just
one function?

Stefan
Mohan Kumar M - March 9, 2011, 8:08 a.m.
On Friday 04 March 2011 4:36:35 pm Stefan Hajnoczi wrote:
> On Fri, Mar 4, 2011 at 9:25 AM, M. Mohan Kumar <mohan@in.ibm.com> wrote:
> > +static int chroot_do_create_special(V9fsFileObjectRequest *request)
> > +{
> > +    int cur_uid, cur_gid;
> > +    int retval = -1;
> > +
> > +    cur_uid = geteuid();
> > +    cur_gid = getegid();
> > +
> > +    if (setfsuid(request->data.uid) < 0) {
> > +        return -errno;
> > +    }
> > +    if (setfsgid(request->data.gid) < 0) {
> > +        retval = -errno;
> > +        goto unset_uid;
> > +    }
> > +
> > +    switch (request->data.type) {
> > +    case T_MKDIR:
> > +        retval = mkdir(request->path.path, request->data.mode);
> > +        break;
> > +    case T_SYMLINK:
> > +        retval = symlink(request->path.old_path, request->path.path);
> > +        break;
> > +    case T_LINK:
> > +        retval = link(request->path.old_path, request->path.path);
> > +        break;
> > +    default:
> > +        retval = mknod(request->path.path, request->data.mode,
> > +                        request->data.dev);
> > +        break;
> > +    }
> > +
> > +    if (retval < 0) {
> > +        retval = -errno;
> > +    }
> > +    setfsgid(cur_gid);
> > +unset_uid:
> > +    setfsuid(cur_uid);
> > +    return retval;
> > +}
> 
> It would be nice to take this one step further and move file create
> and open here too.  The prototype we need is:
> 
> static int chroot_handle_request(V9fsFileObjectRequest *request, int *fd)
> {
>     *fd = -1;
> 
> It returns 0 on success or -errno and *fd >= 0 if a file descriptor
> was opened and -1 otherwise.
> 
> This function becomes the main request processing function called from
> v9fs_chroot() and the switch statement there can be eliminated.
>

We don't need setfsgid, setfsuid for normal open. Also I think having separate 
function based on the functionality helps better code readability. 
 
> Sending the response back to QEMU then gets a cleaned up prototype:
> chroot_sendfd(int chroot_sock, int result, int fd) where result is 0
> on success or -errno and fd >= 0 if present or -1 if not.
> 
> > +int v9fs_create_special(FsContext *fs_ctx, V9fsFileObjectRequest
> > *request) +{
> > +    int retval, sock_error;
> > +    qemu_mutex_lock(&fs_ctx->chroot_mutex);
> > +    if (fs_ctx->chroot_ioerror) {
> > +        retval = -EIO;
> > +        goto unlock;
> > +    }
> > +    if (v9fs_write_request(fs_ctx->chroot_socket, request) < 0) {
> > +        fs_ctx->chroot_ioerror = 1;
> > +        retval = -EIO;
> > +        goto unlock;
> > +    }
> > +    retval = v9fs_receivefd(fs_ctx->chroot_socket, &sock_error);
> > +    if (retval < 0 && sock_error) {
> > +        fs_ctx->chroot_ioerror = 1;
> > +    }
> > +unlock:
> > +    qemu_mutex_unlock(&fs_ctx->chroot_mutex);
> > +    return retval;
> > +}
> 
> This function is a duplicate of v9fs_request().  Can't there be just
> one function?
> 
Yeah, I will make it as a single function.

----
M. Mohan Kumar

Patch

diff --git a/hw/9pfs/virtio-9p-chroot-worker.c b/hw/9pfs/virtio-9p-chroot-worker.c
index cdcb303..fcc0be1 100644
--- a/hw/9pfs/virtio-9p-chroot-worker.c
+++ b/hw/9pfs/virtio-9p-chroot-worker.c
@@ -115,6 +115,52 @@  unset_uid:
     return fd;
 }
 
+/*
+ * Create directory, symbolic link, link, device node and regular files
+ * Similar to create, but it does not return the fd of created object
+ * Returns 0 as file descriptor on success and -errno on failure
+ */
+static int chroot_do_create_special(V9fsFileObjectRequest *request)
+{
+    int cur_uid, cur_gid;
+    int retval = -1;
+
+    cur_uid = geteuid();
+    cur_gid = getegid();
+
+    if (setfsuid(request->data.uid) < 0) {
+        return -errno;
+    }
+    if (setfsgid(request->data.gid) < 0) {
+        retval = -errno;
+        goto unset_uid;
+    }
+
+    switch (request->data.type) {
+    case T_MKDIR:
+        retval = mkdir(request->path.path, request->data.mode);
+        break;
+    case T_SYMLINK:
+        retval = symlink(request->path.old_path, request->path.path);
+        break;
+    case T_LINK:
+        retval = link(request->path.old_path, request->path.path);
+        break;
+    default:
+        retval = mknod(request->path.path, request->data.mode,
+                        request->data.dev);
+        break;
+    }
+
+    if (retval < 0) {
+        retval = -errno;
+    }
+    setfsgid(cur_gid);
+unset_uid:
+    setfsuid(cur_uid);
+    return retval;
+}
+
 static void chroot_daemonize(int chroot_sock)
 {
     sigset_t sigset;
@@ -210,6 +256,12 @@  int v9fs_chroot(FsContext *fs_ctx)
                 valid_fd = 1;
             }
             break;
+        case T_MKDIR:
+        case T_SYMLINK:
+        case T_LINK:
+        case T_MKNOD:
+            fd = chroot_do_create_special(&request);
+            break;
         default:
             fd = -1;
             break;
diff --git a/hw/9pfs/virtio-9p-chroot.c b/hw/9pfs/virtio-9p-chroot.c
index 0c91db6..ff0a53e 100644
--- a/hw/9pfs/virtio-9p-chroot.c
+++ b/hw/9pfs/virtio-9p-chroot.c
@@ -102,3 +102,26 @@  unlock:
     qemu_mutex_unlock(&fs_ctx->chroot_mutex);
     return fd;
 }
+
+/* Return 0 on success or -errno on error */
+int v9fs_create_special(FsContext *fs_ctx, V9fsFileObjectRequest *request)
+{
+    int retval, sock_error;
+    qemu_mutex_lock(&fs_ctx->chroot_mutex);
+    if (fs_ctx->chroot_ioerror) {
+        retval = -EIO;
+        goto unlock;
+    }
+    if (v9fs_write_request(fs_ctx->chroot_socket, request) < 0) {
+        fs_ctx->chroot_ioerror = 1;
+        retval = -EIO;
+        goto unlock;
+    }
+    retval = v9fs_receivefd(fs_ctx->chroot_socket, &sock_error);
+    if (retval < 0 && sock_error) {
+        fs_ctx->chroot_ioerror = 1;
+    }
+unlock:
+    qemu_mutex_unlock(&fs_ctx->chroot_mutex);
+    return retval;
+}
diff --git a/hw/9pfs/virtio-9p-chroot.h b/hw/9pfs/virtio-9p-chroot.h
index 6f676e9..a7f60e2 100644
--- a/hw/9pfs/virtio-9p-chroot.h
+++ b/hw/9pfs/virtio-9p-chroot.h
@@ -40,5 +40,6 @@  typedef struct V9fsFileObjectRequest
 
 int v9fs_chroot(FsContext *fs_ctx);
 int v9fs_request(FsContext *fs_ctx, V9fsFileObjectRequest *or);
+int v9fs_create_special(FsContext *fs_ctx, V9fsFileObjectRequest *request);
 
 #endif /* _QEMU_VIRTIO_9P_CHROOT_H */
diff --git a/hw/9pfs/virtio-9p-local.c b/hw/9pfs/virtio-9p-local.c
index aa8ebff..904ee71 100644
--- a/hw/9pfs/virtio-9p-local.c
+++ b/hw/9pfs/virtio-9p-local.c
@@ -83,6 +83,32 @@  static int passthrough_create(FsContext *fs_ctx, const char *path, int flags,
     return fd;
 }
 
+static int passthrough_create_special(FsContext *fs_ctx, const char *oldpath,
+                const char *path, FsCred *credp, int type)
+{
+    V9fsFileObjectRequest request;
+    int retval;
+
+    retval = fill_fileobjectrequest(&request, path, credp);
+    if (retval < 0) {
+        return retval;
+    }
+    request.data.type = type;
+    if (oldpath) {
+        request.data.oldpath_len = strlen(oldpath);
+        if (strlen(oldpath) >= PATH_MAX) {
+            return -ENAMETOOLONG;
+        }
+        strcpy(request.path.old_path, oldpath);
+    }
+    retval = v9fs_create_special(fs_ctx, &request);
+    if (retval < 0) {
+        errno = -retval;
+        retval = -1;
+    }
+    return retval;
+}
+
 static int local_lstat(FsContext *fs_ctx, const char *path, struct stat *stbuf)
 {
     int err;
@@ -300,8 +326,7 @@  static int local_mknod(FsContext *fs_ctx, const char *path, FsCred *credp)
             serrno = errno;
             goto err_end;
         }
-    } else if ((fs_ctx->fs_sm == SM_PASSTHROUGH) ||
-               (fs_ctx->fs_sm == SM_NONE)) {
+    } else if (fs_ctx->fs_sm == SM_NONE) {
         err = mknod(rpath(fs_ctx, path), credp->fc_mode, credp->fc_rdev);
         if (err == -1) {
             return err;
@@ -311,6 +336,12 @@  static int local_mknod(FsContext *fs_ctx, const char *path, FsCred *credp)
             serrno = errno;
             goto err_end;
         }
+    } else if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        err = passthrough_create_special(fs_ctx, NULL, path, credp, T_MKNOD);
+        if (err < 0) {
+            serrno = errno;
+            goto err_end;
+        }
     }
     return err;
 
@@ -337,8 +368,7 @@  static int local_mkdir(FsContext *fs_ctx, const char *path, FsCred *credp)
             serrno = errno;
             goto err_end;
         }
-    } else if ((fs_ctx->fs_sm == SM_PASSTHROUGH) ||
-               (fs_ctx->fs_sm == SM_NONE)) {
+    } else if (fs_ctx->fs_sm == SM_NONE) {
         err = mkdir(rpath(fs_ctx, path), credp->fc_mode);
         if (err == -1) {
             return err;
@@ -348,6 +378,12 @@  static int local_mkdir(FsContext *fs_ctx, const char *path, FsCred *credp)
             serrno = errno;
             goto err_end;
         }
+    } else if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        err = passthrough_create_special(fs_ctx, NULL, path, credp, T_MKDIR);
+        if (err < 0) {
+            serrno = errno;
+            goto err_end;
+        }
     }
     return err;
 
@@ -465,23 +501,19 @@  static int local_symlink(FsContext *fs_ctx, const char *oldpath,
             serrno = errno;
             goto err_end;
         }
-    } else if ((fs_ctx->fs_sm == SM_PASSTHROUGH) ||
-               (fs_ctx->fs_sm == SM_NONE)) {
+    } else if (fs_ctx->fs_sm == SM_NONE) {
         err = symlink(oldpath, rpath(fs_ctx, newpath));
         if (err) {
             return err;
         }
         err = lchown(rpath(fs_ctx, newpath), credp->fc_uid, credp->fc_gid);
-        if (err == -1) {
-            /*
-             * If we fail to change ownership and if we are
-             * using security model none. Ignore the error
-             */
-            if (fs_ctx->fs_sm != SM_NONE) {
-                serrno = errno;
-                goto err_end;
-            } else
-                err = 0;
+        err = 0;
+    } else if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        err = passthrough_create_special(fs_ctx, oldpath, newpath, credp,
+                        T_SYMLINK);
+        if (err < 0) {
+            serrno = errno;
+            goto err_end;
         }
     }
     return err;
@@ -492,24 +524,27 @@  err_end:
     return err;
 }
 
-static int local_link(FsContext *ctx, const char *oldpath, const char *newpath)
+static int local_link(FsContext *fs_ctx, const char *oldpath,
+                const char *newpath)
 {
-    char *tmp = qemu_strdup(rpath(ctx, oldpath));
     int err, serrno = 0;
 
-    if (tmp == NULL) {
-        return -ENOMEM;
-    }
-
-    err = link(tmp, rpath(ctx, newpath));
-    if (err == -1) {
-        serrno = errno;
-    }
-
-    qemu_free(tmp);
-
-    if (err == -1) {
-        errno = serrno;
+    if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        err = passthrough_create_special(fs_ctx, oldpath, newpath, NULL,
+                        T_LINK);
+        if (err < 0) {
+            serrno = errno;
+        }
+    } else {
+        char *tmp = qemu_strdup(rpath(fs_ctx, oldpath));
+        if (tmp == NULL) {
+            return -ENOMEM;
+        }
+        err = link(tmp, rpath(fs_ctx, newpath));
+        if (err == -1) {
+            serrno = errno;
+        }
+        qemu_free(tmp);
     }
 
     return err;