vfs: don't set FILE_CREATED before calling ->atomic_open() (116cc022) · Commits · 戴 / test

If O_CREAT|O_EXCL are passed to open, then we know that either - the file is successfully created, or - the operation fails in some way. So previously we set FILE_CREATED before calling ->atomic_open() so the filesystem doesn't have to. This, however, led to bugs in the implementation that went unnoticed when the filesystem didn't check for existence, yet returned success. To prevent this kind of bug, require filesystems to always explicitly set FILE_CREATED on O_CREAT|O_EXCL and verify this in the VFS. Also added a couple more verifications for the result of atomic_open(): - Warn if filesystem set FILE_CREATED despite the lack of O_CREAT. - Warn if filesystem set FILE_CREATED but gave a negative dentry. Signed-off-by:

Miklos Szeredi <mszeredi@suse.cz> Signed-off-by:

Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -2656,6 +2656,7 @@ static int atomic_open(struct nameidata nd, struct dentry dentry,
		int acc_mode;
		int create_error = 0;
		struct dentry const DENTRY_NOT_SET = (void ) -1UL;
		bool excl;

		BUG_ON(dentry->d_inode);

		@@ -2669,10 +2670,9 @@ static int atomic_open(struct nameidata nd, struct dentry dentry,
		if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
		mode &= ~current_umask();

		if ((open_flag & (O_EXCL \| O_CREAT)) == (O_EXCL \| O_CREAT)) {
		excl = (open_flag & (O_EXCL \| O_CREAT)) == (O_EXCL \| O_CREAT);
		if (excl)
		open_flag &= ~O_TRUNC;
		*opened \|= FILE_CREATED;
		}

		/*
		* Checking write permission is tricky, bacuse we don't know if we are
		@@ -2726,7 +2726,11 @@ static int atomic_open(struct nameidata nd, struct dentry dentry,
		}

		acc_mode = op->acc_mode;
		if (WARN_ON(excl && !(*opened & FILE_CREATED)))
		*opened \|= FILE_CREATED;

		if (*opened & FILE_CREATED) {
		WARN_ON(!(open_flag & O_CREAT));
		fsnotify_create(dir, dentry);
		acc_mode = MAY_OPEN;
		}
		@@ -2740,6 +2744,7 @@ static int atomic_open(struct nameidata nd, struct dentry dentry,
		dput(dentry);
		dentry = file->f_path.dentry;
		}
		WARN_ON(!dentry->d_inode && (*opened & FILE_CREATED));
		if (create_error && dentry->d_inode == NULL) {
		error = create_error;
		goto out;

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