From d1fe96c0e4de78ba0cd336ea3df3b850d06b9b9a Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Fri, 2 Feb 2018 10:23:24 -0500 Subject: ovl: redirect_dir=nofollow should not follow redirect for opaque lower redirect_dir=nofollow should not follow a redirect. But in a specific configuration it can still follow it. For example try this. $ mkdir -p lower0 lower1/foo upper work merged $ touch lower1/foo/lower-file.txt $ setfattr -n "trusted.overlay.opaque" -v "y" lower1/foo $ mount -t overlay -o lowerdir=lower1:lower0,workdir=work,upperdir=upper,redirect_dir=on none merged $ cd merged $ mv foo foo-renamed $ umount merged # mount again. This time with redirect_dir=nofollow $ mount -t overlay -o lowerdir=lower1:lower0,workdir=work,upperdir=upper,redirect_dir=nofollow none merged $ ls merged/foo-renamed/ # This lists lower-file.txt, while it should not have. Basically, we are doing redirect check after we check for d.stop. And if this is not last lower, and we find an opaque lower, d.stop will be set. ovl_lookup_single() if (!d->last && ovl_is_opaquedir(this)) { d->stop = d->opaque = true; goto out; } To fix this, first check redirect is allowed. And after that check if d.stop has been set or not. Signed-off-by: Vivek Goyal Fixes: 438c84c2f0c7 ("ovl: don't follow redirects if redirect_dir=off") Cc: #v4.15 Signed-off-by: Miklos Szeredi --- fs/overlayfs/namei.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'fs') diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index de3e6da1d5a5..70fcfcc684cc 100644 --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -913,9 +913,6 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, stack[ctr].layer = lower.layer; ctr++; - if (d.stop) - break; - /* * Following redirects can have security consequences: it's like * a symlink into the lower layer without the permission checks. @@ -933,6 +930,9 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, goto out_put; } + if (d.stop) + break; + if (d.redirect && d.redirect[0] == '/' && poe != roe) { poe = roe; /* Find the current layer on the root dentry */ -- cgit v1.2.3-58-ga151