fix

5 files changed, 72 insertions, 9 deletions

diff --git a/ChangeLog b/ChangeLog
index 1800d7d..d2ce216 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2005-04-28  Miklos Szeredi <miklos@szeredi.hu>
+
+	* Check for hard-linked directories in lookup.  This could cause
+	problems in the VFS, which assumes that such objects never exist.
+
+	* Make checking of permission for other users more strict.  Now
+	the same privilege is required for the mount owner as for ptrace
+	on the process performing the filesystem operation.
+	
 2005-04-23  Miklos Szeredi <miklos@szeredi.hu>
 
 	* Released 2.3-pre5
diff --git a/kernel/dir.c b/kernel/dir.c
index 947d538..4f7a83f 100644
--- a/kernel/dir.c
+++ b/kernel/dir.c
@@ -433,17 +433,45 @@ int fuse_do_getattr(struct inode *inode)
 	return err;
 }
 
+static int fuse_allow_task(struct fuse_conn *fc, struct task_struct *task)
+{
+	if (fc->flags & FUSE_ALLOW_OTHER)
+		return 1;
+
+	/* Calling into a user-controlled filesystem gives the
+	   filesystem daemon ptrace-like capabilities over the
+	   requester process.  This means, that the filesystem daemon
+	   is able to record the exact filesystem operations
+	   performed, and can also control the behavior of the
+	   requester process in otherwise impossible ways.  For
+	   example it can delay the operation for arbitrary length of
+	   time allowing DoS against the requester.
+
+	   For this reason only those processes can call into the
+	   filesystem, for which the owner of the mount has ptrace
+	   privilege.  This excludes processes started by other users,
+	   suid or sgid processes. */
+	if (task->euid == fc->user_id &&
+	    task->suid == fc->user_id &&
+	    task->uid == fc->user_id &&
+	    task->egid == fc->group_id &&
+	    task->sgid == fc->group_id &&
+	    task->gid == fc->group_id)
+		return 1;
+
+	return 0;
+}
+
 static int fuse_revalidate(struct dentry *entry)
 {
 	struct inode *inode = entry->d_inode;
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	struct fuse_conn *fc = get_fuse_conn(inode);
 
-	if (get_node_id(inode) == FUSE_ROOT_ID) {
-		if (!(fc->flags & FUSE_ALLOW_OTHER) &&
-		    current->fsuid != fc->user_id)
-			return -EACCES;
-	} else if (time_before_eq(jiffies, fi->i_time))
+	if (!fuse_allow_task(fc, current))
+		return -EACCES;
+	if (get_node_id(inode) != FUSE_ROOT_ID &&
+	    time_before_eq(jiffies, fi->i_time))
 		return 0;
 
 	return fuse_do_getattr(inode);
@@ -453,7 +481,7 @@ static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 
-	if (!(fc->flags & FUSE_ALLOW_OTHER) && current->fsuid != fc->user_id)
+	if (!fuse_allow_task(fc, current))
 		return -EACCES;
 	else if (fc->flags & FUSE_DEFAULT_PERMISSIONS) {
 #ifdef KERNEL_2_6_10_PLUS
@@ -772,6 +800,15 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
 	int err = fuse_lookup_iget(dir, entry, &inode);
 	if (err)
 		return ERR_PTR(err);
+	if (inode && S_ISDIR(inode->i_mode)) {
+		/* Don't allow creating an alias to a directory  */
+		struct dentry *alias = d_find_alias(inode);
+		if (alias && !(alias->d_flags & DCACHE_DISCONNECTED)) {
+			dput(alias);
+			iput(inode);
+			return ERR_PTR(-EIO);
+		}
+	}
 	return d_splice_alias(inode, entry);
 }
 #else /* KERNEL_2_6 */
diff --git a/kernel/fuse_i.h b/kernel/fuse_i.h
index 164eaa7..25724b4 100644
--- a/kernel/fuse_i.h
+++ b/kernel/fuse_i.h
@@ -262,6 +262,9 @@ struct fuse_conn {
 	/** The user id for this mount */
 	uid_t user_id;
 
+	/** The group id for this mount */
+	gid_t group_id;
+
 	/** The fuse mount flags for this mount */
 	unsigned flags;
 
diff --git a/kernel/inode.c b/kernel/inode.c
index 9b894f5..6ef9491 100644
--- a/kernel/inode.c
+++ b/kernel/inode.c
@@ -43,6 +43,7 @@ struct fuse_mount_data {
 	int fd;
 	unsigned rootmode;
 	unsigned user_id;
+	unsigned group_id;
 	unsigned flags;
 	unsigned max_read;
 };
@@ -262,6 +263,7 @@ static void fuse_put_super(struct super_block *sb)
 	spin_lock(&fuse_lock);
 	fc->mounted = 0;
 	fc->user_id = 0;
+	fc->group_id = 0;
 	fc->flags = 0;
 	/* Flush all readers on this fs */
 	wake_up_all(&fc->waitq);
@@ -311,6 +313,7 @@ enum {
 	OPT_FD,
 	OPT_ROOTMODE,
 	OPT_USER_ID,
+	OPT_GROUP_ID,
 	OPT_DEFAULT_PERMISSIONS,
 	OPT_ALLOW_OTHER,
 	OPT_KERNEL_CACHE,
@@ -326,6 +329,7 @@ static match_table_t tokens = {
 	{OPT_FD,			"fd=%u"},
 	{OPT_ROOTMODE,			"rootmode=%o"},
 	{OPT_USER_ID,			"user_id=%u"},
+	{OPT_GROUP_ID,			"group_id=%u"},
 	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},
 	{OPT_ALLOW_OTHER,		"allow_other"},
 	{OPT_KERNEL_CACHE,		"kernel_cache"},
@@ -371,6 +375,12 @@ static int parse_fuse_opt(char *opt, struct fuse_mount_data *d)
 			d->user_id = value;
 			break;
 
+		case OPT_GROUP_ID:
+			if (match_int(&args[0], &value))
+				return 0;
+			d->group_id = value;
+			break;
+
 		case OPT_DEFAULT_PERMISSIONS:
 			d->flags |= FUSE_DEFAULT_PERMISSIONS;
 			break;
@@ -413,6 +423,7 @@ static int fuse_show_options(struct seq_file *m, struct vfsmount *mnt)
 	struct fuse_conn *fc = get_fuse_conn_super(mnt->mnt_sb);
 
 	seq_printf(m, ",user_id=%u", fc->user_id);
+	seq_printf(m, ",group_id=%u", fc->group_id);
 	if (fc->flags & FUSE_DEFAULT_PERMISSIONS)
 		seq_puts(m, ",default_permissions");
 	if (fc->flags & FUSE_ALLOW_OTHER)
@@ -619,6 +630,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 
 	fc->flags = d.flags;
 	fc->user_id = d.user_id;
+	fc->group_id = d.group_id;
 	fc->max_read = d.max_read;
 #ifdef KERNEL_2_6
 	if (fc->max_read / PAGE_CACHE_SIZE < fc->bdi.ra_pages)
diff --git a/util/fusermount.c b/util/fusermount.c
index 1b79446..f55d92b 100644
--- a/util/fusermount.c
+++ b/util/fusermount.c
@@ -491,7 +491,7 @@ static int do_mount(const char *mnt, const char *type, mode_t rootmode,
     char *d;
     char *fsname = NULL;
 
-    optbuf = malloc(strlen(opts) + 64);
+    optbuf = malloc(strlen(opts) + 128);
     if (!optbuf) {
         fprintf(stderr, "%s: failed to allocate memory\n", progname);
         return -1;
@@ -515,7 +515,8 @@ static int do_mount(const char *mnt, const char *type, mode_t rootmode,
             fsname[len - fsname_str_len] = '\0';
         } else if (!begins_with(s, "fd=") &&
                    !begins_with(s, "rootmode=") &&
-                   !begins_with(s, "user_id=")) {
+                   !begins_with(s, "user_id=") &&
+                   !begins_with(s, "group_id=")) {
             int on;
             int flag;
             int skip_option = 0;
@@ -561,7 +562,8 @@ static int do_mount(const char *mnt, const char *type, mode_t rootmode,
         free(optbuf);
         return -1;
     }
-    sprintf(d, "fd=%i,rootmode=%o,user_id=%i", fd, rootmode, getuid());
+    sprintf(d, "fd=%i,rootmode=%o,user_id=%i,group_id=%i",
+            fd, rootmode, getuid(), getgid());
     if (fsname == NULL) {
         fsname = strdup(dev);
         if (!fsname) {