virtio-9p: Use layered xattr approach

We would need this to make sure we handle the mapped
security model correctly for different xattr names.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>

Makefile.objs

@@ -249,7 +249,8 @@ sound-obj-$(CONFIG_CS4231A) += cs4231a.o
 adlib.o fmopl.o: QEMU_CFLAGS += -DBUILD_Y8950=0
 hw-obj-$(CONFIG_SOUND) += $(sound-obj-y)
 
-hw-obj-$(CONFIG_VIRTFS) += virtio-9p-debug.o virtio-9p-local.o
+hw-obj-$(CONFIG_VIRTFS) += virtio-9p-debug.o virtio-9p-local.o virtio-9p-xattr.o
+hw-obj-$(CONFIG_VIRTFS) += virtio-9p-xattr-user.o
 
 ######################################################################
 # libdis

hw/file-op-9p.h

@@ -47,11 +47,14 @@ typedef struct FsCred
     dev_t   fc_rdev;
 } FsCred;
 
+struct xattr_operations;
+
 typedef struct FsContext
 {
     char *fs_root;
     SecModel fs_sm;
     uid_t uid;
+    struct xattr_operations **xops;
 } FsContext;
 
 extern void cred_init(FsCred *);
@@ -94,4 +97,12 @@ typedef struct FileOperations
     int (*lremovexattr)(FsContext *, const char *, const char *);
     void *opaque;
 } FileOperations;
+
+static inline const char *rpath(FsContext *ctx, const char *path)
+{
+    /* FIXME: so wrong... */
+    static char buffer[4096];
+    snprintf(buffer, sizeof(buffer), "%s/%s", ctx->fs_root, path);
+    return buffer;
+}
 #endif

hw/virtio-9p-local.c

@@ -12,6 +12,7 @@
  */
 #include "virtio.h"
 #include "virtio-9p.h"
+#include "virtio-9p-xattr.h"
 #include <arpa/inet.h>
 #include <pwd.h>
 #include <grp.h>
@@ -19,14 +20,6 @@
 #include <sys/un.h>
 #include <attr/xattr.h>
 
-static const char *rpath(FsContext *ctx, const char *path)
-{
-    /* FIXME: so wrong... */
-    static char buffer[4096];
-    snprintf(buffer, sizeof(buffer), "%s/%s", ctx->fs_root, path);
-    return buffer;
-}
-
 
 static int local_lstat(FsContext *fs_ctx, const char *path, struct stat *stbuf)
 {
@@ -497,103 +490,25 @@ static int local_statfs(FsContext *s, const char *path, struct statfs *stbuf)
 static ssize_t local_lgetxattr(FsContext *ctx, const char *path,
                                const char *name, void *value, size_t size)
 {
-    if ((ctx->fs_sm == SM_MAPPED) &&
-        (strncmp(name, "user.virtfs.", 12) == 0)) {
-        /*
-         * Don't allow fetch of user.virtfs namesapce
-         * in case of mapped security
-         */
-        errno = ENOATTR;
-        return -1;
-    }
-
-    return lgetxattr(rpath(ctx, path), name, value, size);
+    return v9fs_get_xattr(ctx, path, name, value, size);
 }
 
 static ssize_t local_llistxattr(FsContext *ctx, const char *path,
                                 void *value, size_t size)
 {
-    ssize_t retval;
-    ssize_t actual_len = 0;
-    char *orig_value, *orig_value_start;
-    char *temp_value, *temp_value_start;
-    ssize_t xattr_len, parsed_len = 0, attr_len;
-
-    if (ctx->fs_sm != SM_MAPPED) {
-        return llistxattr(rpath(ctx, path), value, size);
-    }
-
-    /* Get the actual len */
-    xattr_len = llistxattr(rpath(ctx, path), value, 0);
-
-    /* Now fetch the xattr and find the actual size */
-    orig_value = qemu_malloc(xattr_len);
-    xattr_len = llistxattr(rpath(ctx, path), orig_value, xattr_len);
-
-    /*
-     * For mapped security model drop user.virtfs namespace
-     * from the list
-     */
-    temp_value = qemu_mallocz(xattr_len);
-    temp_value_start = temp_value;
-    orig_value_start = orig_value;
-    while (xattr_len > parsed_len) {
-        attr_len = strlen(orig_value) + 1;
-        if (strncmp(orig_value, "user.virtfs.", 12) != 0) {
-            /* Copy this entry */
-            strcat(temp_value, orig_value);
-            temp_value  += attr_len;
-            actual_len += attr_len;
-        }
-        parsed_len += attr_len;
-        orig_value += attr_len;
-    }
-    if (!size) {
-        retval = actual_len;
-        goto out;
-    } else if (size >= actual_len) {
-        /* now copy the parsed attribute list back */
-        memset(value, 0, size);
-        memcpy(value, temp_value_start, actual_len);
-        retval = actual_len;
-        goto out;
-    }
-    errno = ERANGE;
-    retval = -1;
-out:
-    qemu_free(orig_value_start);
-    qemu_free(temp_value_start);
-    return retval;
+    return v9fs_list_xattr(ctx, path, value, size);
 }
 
 static int local_lsetxattr(FsContext *ctx, const char *path, const char *name,
                            void *value, size_t size, int flags)
 {
-    if ((ctx->fs_sm == SM_MAPPED) &&
-        (strncmp(name, "user.virtfs.", 12) == 0)) {
-        /*
-         * Don't allow fetch of user.virtfs namesapce
-         * in case of mapped security
-         */
-        errno = EACCES;
-        return -1;
-    }
-    return lsetxattr(rpath(ctx, path), name, value, size, flags);
+    return v9fs_set_xattr(ctx, path, name, value, size, flags);
 }
 
 static int local_lremovexattr(FsContext *ctx,
                               const char *path, const char *name)
 {
-    if ((ctx->fs_sm == SM_MAPPED) &&
-        (strncmp(name, "user.virtfs.", 12) == 0)) {
-        /*
-         * Don't allow fetch of user.virtfs namesapce
-         * in case of mapped security
-         */
-        errno = EACCES;
-        return -1;
-    }
-    return lremovexattr(rpath(ctx, path), name);
+    return v9fs_remove_xattr(ctx, path, name);
 }
 
 

hw/virtio-9p-xattr-user.c

+/*
+ * Virtio 9p user. xattr callback
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ * Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include <sys/types.h>
+#include "virtio.h"
+#include "virtio-9p.h"
+#include "file-op-9p.h"
+#include "virtio-9p-xattr.h"
+
+
+static ssize_t mp_user_getxattr(FsContext *ctx, const char *path,
+                                const char *name, void *value, size_t size)
+{
+    if (strncmp(name, "user.virtfs.", 12) == 0) {
+        /*
+         * Don't allow fetch of user.virtfs namesapce
+         * in case of mapped security
+         */
+        errno = ENOATTR;
+        return -1;
+    }
+    return lgetxattr(rpath(ctx, path), name, value, size);
+}
+
+static ssize_t mp_user_listxattr(FsContext *ctx, const char *path,
+                                 char *name, void *value, size_t size)
+{
+    int name_size = strlen(name) + 1;
+    if (strncmp(name, "user.virtfs.", 12) == 0) {
+        /*
+         * Don't allow fetch of user.virtfs namesapce
+         * in case of mapped security
+         */
+        return 0;
+    }
+    if (!value) {
+        return name_size;
+    }
+
+    if (size < name_size) {
+        errno = ERANGE;
+        return -1;
+    }
+
+    strncpy(value, name, name_size);
+    return name_size;
+}
+
+static int mp_user_setxattr(FsContext *ctx, const char *path, const char *name,
+                            void *value, size_t size, int flags)
+{
+    if (strncmp(name, "user.virtfs.", 12) == 0) {
+        /*
+         * Don't allow fetch of user.virtfs namesapce
+         * in case of mapped security
+         */
+        errno = EACCES;
+        return -1;
+    }
+    return lsetxattr(rpath(ctx, path), name, value, size, flags);
+}
+
+static int mp_user_removexattr(FsContext *ctx,
+                               const char *path, const char *name)
+{
+    if (strncmp(name, "user.virtfs.", 12) == 0) {
+        /*
+         * Don't allow fetch of user.virtfs namesapce
+         * in case of mapped security
+         */
+        errno = EACCES;
+        return -1;
+    }
+    return lremovexattr(rpath(ctx, path), name);
+}
+
+XattrOperations mapped_user_xattr = {
+    .name = "user.",
+    .getxattr = mp_user_getxattr,
+    .setxattr = mp_user_setxattr,
+    .listxattr = mp_user_listxattr,
+    .removexattr = mp_user_removexattr,
+};
+
+XattrOperations passthrough_user_xattr = {
+    .name = "user.",
+    .getxattr = pt_getxattr,
+    .setxattr = pt_setxattr,
+    .listxattr = pt_listxattr,
+    .removexattr = pt_removexattr,
+};

hw/virtio-9p-xattr.c

+/*
+ * Virtio 9p  xattr callback
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ * Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "virtio.h"
+#include "virtio-9p.h"
+#include "file-op-9p.h"
+#include "virtio-9p-xattr.h"
+
+
+static XattrOperations *get_xattr_operations(XattrOperations **h,
+                                             const char *name)
+{
+    XattrOperations *xops;
+    for (xops = *(h)++; xops != NULL; xops = *(h)++) {
+        if (!strncmp(name, xops->name, strlen(xops->name))) {
+            return xops;
+        }
+    }
+    return NULL;
+}
+
+ssize_t v9fs_get_xattr(FsContext *ctx, const char *path,
+                       const char *name, void *value, size_t size)
+{
+    XattrOperations *xops = get_xattr_operations(ctx->xops, name);
+    if (xops) {
+        return xops->getxattr(ctx, path, name, value, size);
+    }
+    errno = -EOPNOTSUPP;
+    return -1;
+}
+
+ssize_t pt_listxattr(FsContext *ctx, const char *path,
+                     char *name, void *value, size_t size)
+{
+    int name_size = strlen(name) + 1;
+    if (!value) {
+        return name_size;
+    }
+
+    if (size < name_size) {
+        errno = ERANGE;
+        return -1;
+    }
+
+    strncpy(value, name, name_size);
+    return name_size;
+}
+
+
+/*
+ * Get the list and pass to each layer to find out whether
+ * to send the data or not
+ */
+ssize_t v9fs_list_xattr(FsContext *ctx, const char *path,
+                        void *value, size_t vsize)
+{
+    ssize_t size = 0;
+    void *ovalue = value;
+    XattrOperations *xops;
+    char *orig_value, *orig_value_start;
+    ssize_t xattr_len, parsed_len = 0, attr_len;
+
+    /* Get the actual len */
+    xattr_len = llistxattr(rpath(ctx, path), value, 0);
+
+    /* Now fetch the xattr and find the actual size */
+    orig_value = qemu_malloc(xattr_len);
+    xattr_len = llistxattr(rpath(ctx, path), orig_value, xattr_len);
+
+    /* store the orig pointer */
+    orig_value_start = orig_value;
+    while (xattr_len > parsed_len) {
+        xops = get_xattr_operations(ctx->xops, orig_value);
+        if (!xops) {
+            goto next_entry;
+        }
+
+        if (!value) {
+            size += xops->listxattr(ctx, path, orig_value, value, vsize);
+        } else {
+            size = xops->listxattr(ctx, path, orig_value, value, vsize);
+            if (size < 0) {
+                goto err_out;
+            }
+            value += size;
+            vsize -= size;
+        }
+next_entry:
+        /* Got the next entry */
+        attr_len = strlen(orig_value) + 1;
+        parsed_len += attr_len;
+        orig_value += attr_len;
+    }
+    if (value) {
+        size = value - ovalue;
+    }
+
+err_out:
+    qemu_free(orig_value_start);
+    return size;
+}
+
+int v9fs_set_xattr(FsContext *ctx, const char *path, const char *name,
+                   void *value, size_t size, int flags)
+{
+    XattrOperations *xops = get_xattr_operations(ctx->xops, name);
+    if (xops) {
+        return xops->setxattr(ctx, path, name, value, size, flags);
+    }
+    errno = -EOPNOTSUPP;
+    return -1;
+
+}
+
+int v9fs_remove_xattr(FsContext *ctx,
+                      const char *path, const char *name)
+{
+    XattrOperations *xops = get_xattr_operations(ctx->xops, name);
+    if (xops) {
+        return xops->removexattr(ctx, path, name);
+    }
+    errno = -EOPNOTSUPP;
+    return -1;
+
+}
+
+XattrOperations *mapped_xattr_ops[] = {
+    &mapped_user_xattr,
+    NULL,
+};
+
+XattrOperations *passthrough_xattr_ops[] = {
+    &passthrough_user_xattr,
+    NULL,
+};
+
+/* for .user none model should be same as passthrough */
+XattrOperations *none_xattr_ops[] = {
+    &passthrough_user_xattr,
+    NULL,
+};

hw/virtio-9p-xattr.h

+/*
+ * Virtio 9p
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+#ifndef _QEMU_VIRTIO_9P_XATTR_H
+#define _QEMU_VIRTIO_9P_XATTR_H
+
+#include <attr/xattr.h>
+
+typedef struct xattr_operations
+{
+    const char *name;
+    ssize_t (*getxattr)(FsContext *ctx, const char *path,
+                        const char *name, void *value, size_t size);
+    ssize_t (*listxattr)(FsContext *ctx, const char *path,
+                         char *name, void *value, size_t size);
+    int (*setxattr)(FsContext *ctx, const char *path, const char *name,
+                    void *value, size_t size, int flags);
+    int (*removexattr)(FsContext *ctx,
+                       const char *path, const char *name);
+} XattrOperations;
+
+
+extern XattrOperations mapped_user_xattr;
+extern XattrOperations passthrough_user_xattr;
+
+extern XattrOperations *mapped_xattr_ops[];
+extern XattrOperations *passthrough_xattr_ops[];
+extern XattrOperations *none_xattr_ops[];
+
+extern ssize_t v9fs_get_xattr(FsContext *ctx, const char *path,
+                              const char *name, void *value, size_t size);
+extern ssize_t v9fs_list_xattr(FsContext *ctx, const char *path,
+                               void *value, size_t vsize);
+extern int v9fs_set_xattr(FsContext *ctx, const char *path, const char *name,
+                          void *value, size_t size, int flags);
+extern int v9fs_remove_xattr(FsContext *ctx,
+                             const char *path, const char *name);
+extern ssize_t pt_listxattr(FsContext *ctx, const char *path,
+                            char *name, void *value, size_t size);
+
+static inline ssize_t pt_getxattr(FsContext *ctx, const char *path,
+                                  const char *name, void *value, size_t size)
+{
+    return lgetxattr(rpath(ctx, path), name, value, size);
+}
+
+static inline int pt_setxattr(FsContext *ctx, const char *path,
+                              const char *name, void *value,
+                              size_t size, int flags)
+{
+    return lsetxattr(rpath(ctx, path), name, value, size, flags);
+}
+
+static inline int pt_removexattr(FsContext *ctx,
+                                 const char *path, const char *name)
+{
+    return lremovexattr(rpath(ctx, path), name);
+}
+
+#endif

hw/virtio-9p.c

@@ -17,6 +17,7 @@
 #include "virtio-9p.h"
 #include "fsdev/qemu-fsdev.h"
 #include "virtio-9p-debug.h"
+#include "virtio-9p-xattr.h"
 
 int debug_9p_pdu;
 
@@ -3712,23 +3713,26 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)
     if (!strcmp(fse->security_model, "passthrough")) {
         /* Files on the Fileserver set to client user credentials */
         s->ctx.fs_sm = SM_PASSTHROUGH;
+        s->ctx.xops = passthrough_xattr_ops;
     } else if (!strcmp(fse->security_model, "mapped")) {
         /* Files on the fileserver are set to QEMU credentials.
          * Client user credentials are saved in extended attributes.
          */
         s->ctx.fs_sm = SM_MAPPED;
+        s->ctx.xops = mapped_xattr_ops;
     } else if (!strcmp(fse->security_model, "none")) {
         /*
          * Files on the fileserver are set to QEMU credentials.
          */
         s->ctx.fs_sm = SM_NONE;
-
+        s->ctx.xops = none_xattr_ops;
     } else {
         fprintf(stderr, "Default to security_model=none. You may want"
                 " enable advanced security model using "
                 "security option:\n\t security_model=passthrough \n\t "
                 "security_model=mapped\n");
         s->ctx.fs_sm = SM_NONE;
+        s->ctx.xops = none_xattr_ops;
     }
 
     if (lstat(fse->path, &stat)) {