Patch "ovl: filter trusted xattr for non-admin" has been added to the 4.9-stable tree

Patch "ovl: filter trusted xattr for non-admin" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    ovl: filter trusted xattr for non-admin

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ovl-filter-trusted-xattr-for-non-admin.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon Apr  9 17:09:24 CEST 2018
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Mon, 29 May 2017 15:15:27 +0200
Subject: ovl: filter trusted xattr for non-admin

From: Miklos Szeredi <mszeredi@redhat.com>


[ Upstream commit a082c6f680da298cf075886ff032f32ccb7c5e1a ]

Filesystems filter out extended attributes in the "trusted." domain for
unprivlieged callers.

Overlay calls underlying filesystem's method with elevated privs, so need
to do the filtering in overlayfs too.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/overlayfs/inode.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -227,6 +227,16 @@ int ovl_xattr_get(struct dentry *dentry,
 	return res;
 }
 
+static bool ovl_can_list(const char *s)
+{
+	/* List all non-trusted xatts */
+	if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0)
+		return true;
+
+	/* Never list trusted.overlay, list other trusted for superuser only */
+	return !ovl_is_private_xattr(s) && capable(CAP_SYS_ADMIN);
+}
+
 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
 {
 	struct dentry *realdentry = ovl_dentry_real(dentry);
@@ -250,7 +260,7 @@ ssize_t ovl_listxattr(struct dentry *den
 			return -EIO;
 
 		len -= slen;
-		if (ovl_is_private_xattr(s)) {
+		if (!ovl_can_list(s)) {
 			res -= slen;
 			memmove(s, s + slen, len);
 		} else {


Patches currently in stable-queue which might be from mszeredi@redhat.com are

queue-4.9/ovl-persistent-inode-numbers-for-upper-hardlinks.patch
queue-4.9/ovl-filter-trusted-xattr-for-non-admin.patch