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Commit b0990fbb authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
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ovl: check IS_APPEND() on real upper inode 



For overlay file open, check IS_APPEND() on the real upper inode
inside d_real(), because the overlay inode does not have the
S_APPEND flag and IS_APPEND() can only be checked at open time.

Note that because overlayfs does not copy up the chattr inode flags
(i.e. S_APPEND, S_IMMUTABLE), the IS_APPEND() check is only relevant
for upper inodes that were set with chattr +a and not to lower
inodes that had chattr +a before copy up.

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 78757af6

fs/overlayfs/super.c

+25 −3
Original line number Diff line number Diff line
@@ -49,11 +49,28 @@ static void ovl_dentry_release(struct dentry *dentry) 
	}

}



static int ovl_check_append_only(struct inode *inode, int flag)

{

	/*

	 * This test was moot in vfs may_open() because overlay inode does

	 * not have the S_APPEND flag, so re-check on real upper inode

	 */

	if (IS_APPEND(inode)) {

		if  ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))

			return -EPERM;

		if (flag & O_TRUNC)

			return -EPERM;

	}



	return 0;

}



static struct dentry *ovl_d_real(struct dentry *dentry,

				 const struct inode *inode,

				 unsigned int open_flags)

{

	struct dentry *real;

	int err;



	if (!d_is_reg(dentry)) {

		if (!inode || inode == d_inode(dentry))
@@ -65,15 +82,20 @@ static struct dentry *ovl_d_real(struct dentry *dentry, 
		return dentry;



	if (open_flags) {

		int err = ovl_open_maybe_copy_up(dentry, open_flags);



		err = ovl_open_maybe_copy_up(dentry, open_flags);

		if (err)

			return ERR_PTR(err);

	}



	real = ovl_dentry_upper(dentry);

	if (real && (!inode || inode == d_inode(real)))

	if (real && (!inode || inode == d_inode(real))) {

		if (!inode) {

			err = ovl_check_append_only(d_inode(real), open_flags);

			if (err)

				return ERR_PTR(err);

		}

		return real;

	}



	real = ovl_dentry_lower(dentry);

	if (!real)