ecryptfs: use vfs_get_link() (6c988f57) · Commits · 戴 / test

Here again we are copying form one buffer to another, while jumping through hoops to make kernel memory look like userspace memory. For no good reason, since vfs_get_link() provides exactly what is needed. As a bonus, now the security hook for readlink is also called on the underlying inode. Note: this can be called from link-following context. But this is okay: - not in RCU mode - commit ("proc: prevent stacking filesystems on top") - ecryptfs is *reading* the underlying symlink not following it, so the right security hook is being called Signed-off-by:

Miklos Szeredi <mszeredi@redhat.com> Cc: Tyler Hicks <tyhicks@canonical.com>

fs/ecryptfs/inode.c

+12 −17

Original line number	Diff line number	Diff line
		@@ -631,28 +631,23 @@ out_lock:

		static char ecryptfs_readlink_lower(struct dentry dentry, size_t *bufsiz)
		{
		DEFINE_DELAYED_CALL(done);
		struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
		char *lower_buf;
		const char *link;
		char *buf;
		mm_segment_t old_fs;
		int rc;

		lower_buf = kmalloc(PATH_MAX, GFP_KERNEL);
		if (!lower_buf)
		return ERR_PTR(-ENOMEM);
		old_fs = get_fs();
		set_fs(get_ds());
		rc = d_inode(lower_dentry)->i_op->readlink(lower_dentry,
		(char __user *)lower_buf,
		PATH_MAX);
		set_fs(old_fs);
		if (rc < 0)
		goto out;
		link = vfs_get_link(lower_dentry, &done);
		if (IS_ERR(link))
		return ERR_CAST(link);

		rc = ecryptfs_decode_and_decrypt_filename(&buf, bufsiz, dentry->d_sb,
		lower_buf, rc);
		out:
		kfree(lower_buf);
		return rc ? ERR_PTR(rc) : buf;
		link, strlen(link));
		do_delayed_call(&done);
		if (rc)
		return ERR_PTR(rc);

		return buf;
		}

		static const char ecryptfs_get_link(struct dentry dentry,

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