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Commit 7715b521 authored by Al Viro's avatar Al Viro
Browse files

O_TRUNC open shouldn't fail after file truncation 



* take truncate logics into a helper (handle_truncate())
* rip it out of may_open()
* call it from the only caller of may_open() that might pass
O_TRUNC
* and do that after we'd finished with opening.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 85a17f55

fs/namei.c

+56 −53
Original line number Diff line number Diff line
@@ -1444,43 +1444,39 @@ int may_open(struct path *path, int acc_mode, int flag) 
	if (error)

		return error;



	error = ima_path_check(path, acc_mode ?

			       acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC) :

			       ACC_MODE(flag) & (MAY_READ | MAY_WRITE),

			       IMA_COUNT_UPDATE);



	if (error)

		return error;

	/*

	 * An append-only file must be opened in append mode for writing.

	 */

	if (IS_APPEND(inode)) {

		error = -EPERM;

		if  ((flag & FMODE_WRITE) && !(flag & O_APPEND))

			goto err_out;

			return -EPERM;

		if (flag & O_TRUNC)

			goto err_out;

			return -EPERM;

	}



	/* O_NOATIME can only be set by the owner or superuser */

	if (flag & O_NOATIME)

		if (!is_owner_or_cap(inode)) {

			error = -EPERM;

			goto err_out;

		}

	if (flag & O_NOATIME && !is_owner_or_cap(inode))

		return -EPERM;



	/*

	 * Ensure there are no outstanding leases on the file.

	 */

	error = break_lease(inode, flag);

	if (error)

		goto err_out;

		return error;



	if (flag & O_TRUNC) {

		error = get_write_access(inode);

		if (error)

			goto err_out;

	return ima_path_check(path, acc_mode ?

			       acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC) :

			       ACC_MODE(flag) & (MAY_READ | MAY_WRITE),

			       IMA_COUNT_UPDATE);

}



static int handle_truncate(struct path *path)

{

	struct inode *inode = path->dentry->d_inode;

	int error = get_write_access(inode);

	if (error)

		return error;

	/*

	 * Refuse to truncate files with mandatory locks held on them.

	 */
@@ -1489,24 +1485,11 @@ int may_open(struct path *path, int acc_mode, int flag) 
		error = security_path_truncate(path, 0,

				       ATTR_MTIME|ATTR_CTIME|ATTR_OPEN);

	if (!error) {

			vfs_dq_init(inode);



			error = do_truncate(dentry, 0,

		error = do_truncate(path->dentry, 0,

				    ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,

				    NULL);

	}

	put_write_access(inode);

		if (error)

			goto err_out;

	} else

		if (flag & FMODE_WRITE)

			vfs_dq_init(inode);



	return 0;

err_out:

	ima_counts_put(path, acc_mode ?

		       acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC) :

		       ACC_MODE(flag) & (MAY_READ | MAY_WRITE));

	return error;

}
@@ -1561,7 +1544,7 @@ static inline int open_to_namei_flags(int flag) 
	return flag;

}



static int open_will_write_to_fs(int flag, struct inode *inode)

static int open_will_truncate(int flag, struct inode *inode)

{

	/*

	 * We'll never write to the fs underlying
@@ -1586,7 +1569,7 @@ struct file *do_filp_open(int dfd, const char *pathname, 
	struct path path, save;

	struct dentry *dir;

	int count = 0;

	int will_write;

	int will_truncate;

	int flag = open_to_namei_flags(open_flag);



	/*
@@ -1752,28 +1735,48 @@ struct file *do_filp_open(int dfd, const char *pathname, 
	 * 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) {

	will_truncate = open_will_truncate(flag, nd.path.dentry->d_inode);

	if (will_truncate) {

		error = mnt_want_write(nd.path.mnt);

		if (error)

			goto exit;

	}

	error = may_open(&nd.path, acc_mode, flag);

	if (error) {

		if (will_write)

		if (will_truncate)

			mnt_drop_write(nd.path.mnt);

		goto exit;

	}

	filp = nameidata_to_filp(&nd, open_flag);

	if (IS_ERR(filp))

	if (IS_ERR(filp)) {

		ima_counts_put(&nd.path,

			       acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC));

		if (will_truncate)

			mnt_drop_write(nd.path.mnt);

		if (nd.root.mnt)

			path_put(&nd.root);

		return filp;

	}



	if (acc_mode & MAY_WRITE)

		vfs_dq_init(nd.path.dentry->d_inode);



	if (will_truncate) {

		error = handle_truncate(&nd.path);

		if (error) {

			mnt_drop_write(nd.path.mnt);

			fput(filp);

			if (nd.root.mnt)

				path_put(&nd.root);

			return ERR_PTR(error);

		}

	}

	/*

	 * It is now safe to drop the mnt write

	 * because the filp has had a write taken

	 * on its behalf.

	 */

	if (will_write)

	if (will_truncate)

		mnt_drop_write(nd.path.mnt);

	if (nd.root.mnt)

		path_put(&nd.root);