Commit 130fdbc3 authored Jun 02, 2020 by Miklos Szeredi

ovl: pass correct flags for opening real directory



The three instances of ovl_path_open() in overlayfs/readdir.c do three
different things:

 - pass f_flags from overlay file
 - pass O_RDONLY | O_DIRECTORY
 - pass just O_RDONLY

The value of f_flags can be (other than O_RDONLY):

O_WRONLY	- not possible for a directory
O_RDWR		- not possible for a directory
O_CREAT		- masked out by dentry_open()
O_EXCL		- masked out by dentry_open()
O_NOCTTY	- masked out by dentry_open()
O_TRUNC		- masked out by dentry_open()
O_APPEND	- no effect on directory ops
O_NDELAY	- no effect on directory ops
O_NONBLOCK	- no effect on directory ops
__O_SYNC	- no effect on directory ops
O_DSYNC		- no effect on directory ops
FASYNC		- no effect on directory ops
O_DIRECT	- no effect on directory ops
O_LARGEFILE	- ?
O_DIRECTORY	- only affects lookup
O_NOFOLLOW	- only affects lookup
O_NOATIME	- overlay sets this unconditionally in ovl_path_open()
O_CLOEXEC	- only affects fd allocation
O_PATH		- no effect on directory ops
__O_TMPFILE	- not possible for a directory


Fon non-merge directories we use the underlying filesystem's iterate; in
this case honor O_LARGEFILE from the original file to make sure that open
doesn't get rejected.

For merge directories it's safe to pass O_LARGEFILE unconditionally since
userspace will only see the artificial offsets created by overlayfs.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

parent 21d8d66a

fs/overlayfs/readdir.c

+9 −3

Original line number	Diff line number	Diff line
		@@ -297,7 +297,7 @@ static inline int ovl_dir_read(struct path *realpath,
		struct file *realfile;
		int err;

		realfile = ovl_path_open(realpath, O_RDONLY \| O_DIRECTORY);
		realfile = ovl_path_open(realpath, O_RDONLY \| O_LARGEFILE);
		if (IS_ERR(realfile))
		return PTR_ERR(realfile);

		@@ -831,6 +831,12 @@ out_unlock:
		return res;
		}

		static struct file ovl_dir_open_realfile(struct file file,
		struct path *realpath)
		{
		return ovl_path_open(realpath, O_RDONLY \| (file->f_flags & O_LARGEFILE));
		}

		static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
		int datasync)
		{
		@@ -853,7 +859,7 @@ static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
		struct path upperpath;

		ovl_path_upper(dentry, &upperpath);
		realfile = ovl_path_open(&upperpath, O_RDONLY);
		realfile = ovl_dir_open_realfile(file, &upperpath);

		inode_lock(inode);
		if (!od->upperfile) {
		@@ -904,7 +910,7 @@ static int ovl_dir_open(struct inode inode, struct file file)
		return -ENOMEM;

		type = ovl_path_real(file->f_path.dentry, &realpath);
		realfile = ovl_path_open(&realpath, file->f_flags);
		realfile = ovl_dir_open_realfile(file, &realpath);
		if (IS_ERR(realfile)) {
		kfree(od);
		return PTR_ERR(realfile);

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