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ovl: verify upper dentry in ovl_remove_and_whiteout() 

The upper dentry may become stale before we call ovl_lock_rename_workdir.
For example, someone could (mistakenly or maliciously) manually unlink(2)
it directly from upperdir.

To ensure it is not stale, let's lookup it after ovl_lock_rename_workdir
and and check if it matches the upper dentry.

Essentially, it is the same problem and similar solution as in
commit 11f3710417 ("ovl: verify upper dentry before unlink and rename").

Signed-off-by: Maxim Patlasov <mpatlasov@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
This commit is contained in:
Maxim Patlasov 2016-07-21 18:24:26 -07:00 committed by Miklos Szeredi
parent 07a2daab49
commit cfc9fde0b0
1 changed files with 24 additions and 30 deletions
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54
fs/overlayfs/dir.c
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@ -505,6 +505,7 @@ static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
struct dentry *upper;
struct dentry *opaquedir = NULL;
int err;
int flags = 0;
if (WARN_ON(!workdir))
return -EROFS;
@ -534,46 +535,39 @@ static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
if (err)
goto out_dput;
upper = lookup_one_len(dentry->d_name.name, upperdir,
dentry->d_name.len);
err = PTR_ERR(upper);
if (IS_ERR(upper))
goto out_unlock;
err = -ESTALE;
if ((opaquedir && upper != opaquedir) ||
(!opaquedir && ovl_dentry_upper(dentry) &&
upper != ovl_dentry_upper(dentry))) {
goto out_dput_upper;
}
whiteout = ovl_whiteout(workdir, dentry);
err = PTR_ERR(whiteout);
if (IS_ERR(whiteout))
goto out_unlock;
goto out_dput_upper;
upper = ovl_dentry_upper(dentry);
if (!upper) {
upper = lookup_one_len(dentry->d_name.name, upperdir,
dentry->d_name.len);
err = PTR_ERR(upper);
if (IS_ERR(upper))
goto kill_whiteout;
if (d_is_dir(upper))
flags = RENAME_EXCHANGE;
err = ovl_do_rename(wdir, whiteout, udir, upper, 0);
dput(upper);
if (err)
goto kill_whiteout;
} else {
int flags = 0;
err = ovl_do_rename(wdir, whiteout, udir, upper, flags);
if (err)
goto kill_whiteout;
if (flags)
ovl_cleanup(wdir, upper);
if (opaquedir)
upper = opaquedir;
err = -ESTALE;
if (upper->d_parent != upperdir)
goto kill_whiteout;
if (is_dir)
flags |= RENAME_EXCHANGE;
err = ovl_do_rename(wdir, whiteout, udir, upper, flags);
if (err)
goto kill_whiteout;
if (is_dir)
ovl_cleanup(wdir, upper);
}
ovl_dentry_version_inc(dentry->d_parent);
out_d_drop:
d_drop(dentry);
dput(whiteout);
out_dput_upper:
dput(upper);
out_unlock:
unlock_rename(workdir, upperdir);
out_dput: