linux-kernel - [PATCH 5.8 063/255] hugetlbfs: prevent filesystem stacking of hugetlbfs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200901151003.744842719@linuxfoundation.org>
Date:   Tue,  1 Sep 2020 17:08:39 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+d6ec23007e951dadf3de@...kaller.appspotmail.com,
        Amir Goldstein <amir73il@...il.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Matthew Wilcox <willy@...radead.org>,
        Colin Walters <walters@...bum.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.8 063/255] hugetlbfs: prevent filesystem stacking of hugetlbfs

From: Mike Kravetz <mike.kravetz@...cle.com>

[ Upstream commit 15568299b7d9988063afce60731df605ab236e2a ]

syzbot found issues with having hugetlbfs on a union/overlay as reported
in [1].  Due to the limitations (no write) and special functionality of
hugetlbfs, it does not work well in filesystem stacking.  There are no
know use cases for hugetlbfs stacking.  Rather than making modifications
to get hugetlbfs working in such environments, simply prevent stacking.

[1] https://lore.kernel.org/linux-mm/000000000000b4684e05a2968ca6@google.com/

Reported-by: syzbot+d6ec23007e951dadf3de@...kaller.appspotmail.com
Suggested-by: Amir Goldstein <amir73il@...il.com>
Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Acked-by: Miklos Szeredi <mszeredi@...hat.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Colin Walters <walters@...bum.org>
Link: http://lkml.kernel.org/r/80f869aa-810d-ef6c-8888-b46cee135907@oracle.com
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/hugetlbfs/inode.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index ef5313f9c78fe..f936bcf02cce7 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -1364,6 +1364,12 @@ hugetlbfs_fill_super(struct super_block *sb, struct fs_context *fc)
 	sb->s_magic = HUGETLBFS_MAGIC;
 	sb->s_op = &hugetlbfs_ops;
 	sb->s_time_gran = 1;
+
+	/*
+	 * Due to the special and limited functionality of hugetlbfs, it does
+	 * not work well as a stacking filesystem.
+	 */
+	sb->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
 	sb->s_root = d_make_root(hugetlbfs_get_root(sb, ctx));
 	if (!sb->s_root)
 		goto out_free;
-- 
2.25.1