ext4: enforce the immutable flag on open files (02b016ca) · Commits · 戴 / test

According to the chattr man page, "a file with the 'i' attribute cannot be modified..." Historically, this was only enforced when the file was opened, per the rest of the description, "... and the file can not be opened in write mode". There is general agreement that we should standardize all file systems to prevent modifications even for files that were opened at the time the immutable flag is set. Eventually, a change to enforce this at the VFS layer should be landing in mainline. Until then, enforce this at the ext4 level to prevent xfstests generic/553 from failing. Signed-off-by:

Theodore Ts'o <tytso@mit.edu> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: stable@kernel.org

fs/ext4/file.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -165,6 +165,10 @@ static ssize_t ext4_write_checks(struct kiocb iocb, struct iov_iter from)
		ret = generic_write_checks(iocb, from);
		if (ret <= 0)
		return ret;

		if (unlikely(IS_IMMUTABLE(inode)))
		return -EPERM;

		/*
		* If we have encountered a bitmap-format file, the size limit
		* is smaller than s_maxbytes, which is for extent-mapped files.

fs/ext4/inode.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -5520,6 +5520,14 @@ int ext4_setattr(struct dentry dentry, struct iattr attr)
		if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
		return -EIO;

		if (unlikely(IS_IMMUTABLE(inode)))
		return -EPERM;

		if (unlikely(IS_APPEND(inode) &&
		(ia_valid & (ATTR_MODE \| ATTR_UID \|
		ATTR_GID \| ATTR_TIMES_SET))))
		return -EPERM;

		error = setattr_prepare(dentry, attr);
		if (error)
		return error;
		@@ -6194,6 +6202,9 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
		get_block_t *get_block;
		int retries = 0;

		if (unlikely(IS_IMMUTABLE(inode)))
		return VM_FAULT_SIGBUS;

		sb_start_pagefault(inode->i_sb);
		file_update_time(vma->vm_file);

Admin message