Commit 3428030d authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
Browse files

ovl: fix missing upper fs freeze protection on copy up for ioctl 



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: dab5ca8f ("ovl: add lsattr/chattr support")
Cc: <stable@vger.kernel.org> # v4.19
Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Acked-by: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent e93c9c99

fs/overlayfs/copy_up.c

+3 −3
Original line number Diff line number Diff line
@@ -909,14 +909,14 @@ static bool ovl_open_need_copy_up(struct dentry *dentry, int flags) 
	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);

		}

	}

fs/overlayfs/file.c

+2 −3
Original line number Diff line number Diff line
@@ -116,11 +116,10 @@ static int ovl_real_fdget(const struct file *file, struct fd *real) 


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, unsigned int cmd, unsigned long arg) 
		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);

fs/overlayfs/overlayfs.h

+1 −1
Original line number Diff line number Diff line
@@ -421,7 +421,7 @@ extern const struct file_operations ovl_file_operations; 
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);

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