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ovl: fix permission checking for setattr

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[Al Viro] The bug is in being too enthusiastic about optimizing ->setattr()
away - instead of "copy verbatim with metadata" + "chmod/chown/utimes"
(with the former being always safe and the latter failing in case of
insufficient permissions) it tries to combine these two.  Note that copyup
itself will have to do ->setattr() anyway; _that_ is where the elevated
capabilities are right.  Having these two ->setattr() (one to set verbatim
copy of metadata, another to do what overlayfs ->setattr() had been asked
to do in the first place) combined is where it breaks.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Miklos Szeredi 2015-12-04 19:18:48 +01:00 committed by Al Viro
parent 31ade3b83e
commit acff81ec2c
1 changed files with 4 additions and 4 deletions
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8
fs/overlayfs/inode.c
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@ -49,13 +49,13 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr)
if (err)
goto out;
upperdentry = ovl_dentry_upper(dentry);
if (upperdentry) {
err = ovl_copy_up(dentry);
if (!err) {
upperdentry = ovl_dentry_upper(dentry);
mutex_lock(&upperdentry->d_inode->i_mutex);
err = notify_change(upperdentry, attr, NULL);
mutex_unlock(&upperdentry->d_inode->i_mutex);
} else {
err = ovl_copy_up_last(dentry, attr, false);
}
ovl_drop_write(dentry);
out: