[PATCH 5.1 068/122] ovl: fix missing upper fs freeze protection on copy up for ioctl

Greg Kroah-Hartman
2019-05-23T19:29:23Z

From: Amir Goldstein <amir73il@gmail.com>

commit 3428030da004a1128cbdcf93dc03e16f184d845b upstream.

Generalize the helper ovl_open_maybe_copy_up() and use it to copy up file
with data before FS_IOC_SETFLAGS ioctl.

The FS_IOC_SETFLAGS ioctl is a bit of an odd ball in vfs, which probably
caused the confusion. File may be open O_RDONLY, but ioctl modifies the
file. VFS does not call mnt_want_write_file() nor lock inode mutex, but
fs-specific code for FS_IOC_SETFLAGS does. So ovl_ioctl() calls
mnt_want_write_file() for the overlay file, and fs-specific code calls
mnt_want_write_file() for upper fs file, but there was no call for
ovl_want_write() for copy up duration which prevents overlayfs from copying
up on a frozen upper fs.

Fixes: dab5ca8fd9dd ("ovl: add lsattr/chattr support")
Cc: <stable@vger.kernel.org> # v4.19
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/overlayfs/copy_up.c | 6 +++---
fs/overlayfs/file.c | 5 ++---
fs/overlayfs/overlayfs.h | 2 +-
3 files changed, 6 insertions(+), 7 deletions(-)

--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -909,14 +909,14 @@ static bool ovl_open_need_copy_up(struct
return true;
}

-int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
+int ovl_maybe_copy_up(struct dentry *dentry, int flags)
{
int err = 0;

- if (ovl_open_need_copy_up(dentry, file_flags)) {
+ if (ovl_open_need_copy_up(dentry, flags)) {
err = ovl_want_write(dentry);
if (!err) {
- err = ovl_copy_up_flags(dentry, file_flags);
+ err = ovl_copy_up_flags(dentry, flags);
ovl_drop_write(dentry);
}
}
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -116,11 +116,10 @@ static int ovl_real_fdget(const struct f

static int ovl_open(struct inode *inode, struct file *file)
{
- struct dentry *dentry = file_dentry(file);
struct file *realfile;
int err;

- err = ovl_open_maybe_copy_up(dentry, file->f_flags);
+ err = ovl_maybe_copy_up(file_dentry(file), file->f_flags);
if (err)
return err;

@@ -390,7 +389,7 @@ static long ovl_ioctl(struct file *file,
if (ret)
return ret;

- ret = ovl_copy_up_with_data(file_dentry(file));
+ ret = ovl_maybe_copy_up(file_dentry(file), O_WRONLY);
if (!ret) {
ret = ovl_real_ioctl(file, cmd, arg);

--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -421,7 +421,7 @@ extern const struct file_operations ovl_
int ovl_copy_up(struct dentry *dentry);
int ovl_copy_up_with_data(struct dentry *dentry);
int ovl_copy_up_flags(struct dentry *dentry, int flags);
-int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags);
+int ovl_maybe_copy_up(struct dentry *dentry, int flags);
int ovl_copy_xattr(struct dentry *old, struct dentry *new);
int ovl_set_attr(struct dentry *upper, struct kstat *stat);
struct ovl_fh *ovl_encode_real_fh(struct dentry *real, bool is_upper);