X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;ds=sidebyside;f=fs%2Fnamei.c;h=32fd9655485b7fc9b8c8616ad6a61f6ac243b328;hb=f8a87d89304c1eea8e4a8dc02d134f57590913c6;hp=83c843b3fea31fa8d95897cd6b4e9c85fe8aa288;hpb=9079b1eb1753f217c3de9f1b7dd7fd549cc3f0cf;p=linux-2.6

diff --git a/fs/namei.c b/fs/namei.c
index 83c843b3fe..32fd965548 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -30,6 +30,7 @@
 #include <linux/capability.h>
 #include <linux/file.h>
 #include <linux/fcntl.h>
+#include <linux/device_cgroup.h>
 #include <asm/namei.h>
 #include <asm/uaccess.h>
 
@@ -281,6 +282,10 @@ int permission(struct inode *inode, int mask, struct nameidata *nd)
 	if (retval)
 		return retval;
 
+	retval = devcgroup_inode_permission(inode, mask);
+	if (retval)
+		return retval;
+
 	return security_inode_permission(inode, mask, nd);
 }
 
@@ -1623,8 +1628,7 @@ int may_open(struct nameidata *nd, int acc_mode, int flag)
 			return -EACCES;
 
 		flag &= ~O_TRUNC;
-	} else if (IS_RDONLY(inode) && (acc_mode & MAY_WRITE))
-		return -EROFS;
+	}
 
 	error = vfs_permission(nd, acc_mode);
 	if (error)
@@ -1724,18 +1728,32 @@ static inline int open_to_namei_flags(int flag)
 	return flag;
 }
 
+static int open_will_write_to_fs(int flag, struct inode *inode)
+{
+	/*
+	 * We'll never write to the fs underlying
+	 * a device file.
+	 */
+	if (special_file(inode->i_mode))
+		return 0;
+	return (flag & O_TRUNC);
+}
+
 /*
- * Note that the low bits of "flag" aren't the same as in the open
- * system call.  See open_to_namei_flags().
+ * Note that the low bits of the passed in "open_flag"
+ * are not the same as in the local variable "flag". See
+ * open_to_namei_flags() for more details.
  */
 struct file *do_filp_open(int dfd, const char *pathname,
 		int open_flag, int mode)
 {
+	struct file *filp;
 	struct nameidata nd;
 	int acc_mode, error;
 	struct path path;
 	struct dentry *dir;
 	int count = 0;
+	int will_write;
 	int flag = open_to_namei_flags(open_flag);
 
 	acc_mode = ACC_MODE(flag);
@@ -1791,17 +1809,30 @@ do_last:
 	}
 
 	if (IS_ERR(nd.intent.open.file)) {
-		mutex_unlock(&dir->d_inode->i_mutex);
 		error = PTR_ERR(nd.intent.open.file);
-		goto exit_dput;
+		goto exit_mutex_unlock;
 	}
 
 	/* Negative dentry, just create the file */
 	if (!path.dentry->d_inode) {
-		error = __open_namei_create(&nd, &path, flag, mode);
+		/*
+		 * This write is needed to ensure that a
+		 * ro->rw transition does not occur between
+		 * the time when the file is created and when
+		 * a permanent write count is taken through
+		 * the 'struct file' in nameidata_to_filp().
+		 */
+		error = mnt_want_write(nd.path.mnt);
 		if (error)
+			goto exit_mutex_unlock;
+		error = __open_namei_create(&nd, &path, flag, mode);
+		if (error) {
+			mnt_drop_write(nd.path.mnt);
 			goto exit;
-		return nameidata_to_filp(&nd, open_flag);
+		}
+		filp = nameidata_to_filp(&nd, open_flag);
+		mnt_drop_write(nd.path.mnt);
+		return filp;
 	}
 
 	/*
@@ -1831,11 +1862,40 @@ do_last:
 	if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode))
 		goto exit;
 ok:
+	/*
+	 * Consider:
+	 * 1. may_open() truncates a file
+	 * 2. a rw->ro mount transition occurs
+	 * 3. nameidata_to_filp() fails due to
+	 *    the ro mount.
+	 * That would be inconsistent, and should
+	 * be avoided. Taking this mnt write here
+	 * ensures that (2) can not occur.
+	 */
+	will_write = open_will_write_to_fs(flag, nd.path.dentry->d_inode);
+	if (will_write) {
+		error = mnt_want_write(nd.path.mnt);
+		if (error)
+			goto exit;
+	}
 	error = may_open(&nd, acc_mode, flag);
-	if (error)
+	if (error) {
+		if (will_write)
+			mnt_drop_write(nd.path.mnt);
 		goto exit;
-	return nameidata_to_filp(&nd, open_flag);
+	}
+	filp = nameidata_to_filp(&nd, open_flag);
+	/*
+	 * It is now safe to drop the mnt write
+	 * because the filp has had a write taken
+	 * on its behalf.
+	 */
+	if (will_write)
+		mnt_drop_write(nd.path.mnt);
+	return filp;
 
+exit_mutex_unlock:
+	mutex_unlock(&dir->d_inode->i_mutex);
 exit_dput:
 	path_put_conditional(&path, &nd);
 exit:
@@ -1973,6 +2033,10 @@ int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
 	if (!dir->i_op || !dir->i_op->mknod)
 		return -EPERM;
 
+	error = devcgroup_inode_mknod(mode, dev);
+	if (error)
+		return error;
+
 	error = security_inode_mknod(dir, dentry, mode, dev);
 	if (error)
 		return error;