From: Eric W. Biederman Date: Wed, 29 Nov 2017 23:29:20 +0000 (-0600) Subject: userns: Don't fail follow_automount based on s_user_ns X-Git-Tag: v4.15.11~62 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=52e0006fb425c756a4d2ead03677bd675cd0aadb;p=thirdparty%2Fkernel%2Fstable.git userns: Don't fail follow_automount based on s_user_ns [ Upstream commit bbc3e471011417598e598707486f5d8814ec9c01 ] When vfs_submount was added the test to limit automounts from filesystems that with s_user_ns != &init_user_ns accidentially left in follow_automount. The test was never about any security concerns and was always about how do we implement this for filesystems whose s_user_ns != &init_user_ns. At the moment this check makes no difference as there are no filesystems that both set FS_USERNS_MOUNT and implement d_automount. Remove this check now while I am thinking about it so there will not be odd booby traps for someone who does want to make this combination work. vfs_submount still needs improvements to allow this combination to work, and vfs_submount contains a check that presents a warning. The autofs4 filesystem could be modified to set FS_USERNS_MOUNT and it would need not work on this code path, as userspace performs the mounts. Fixes: 93faccbbfa95 ("fs: Better permission checking for submounts") Fixes: aeaa4a79ff6a ("fs: Call d_automount with the filesystems creds") Acked-by: Ian Kent Signed-off-by: "Eric W. Biederman" Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/namei.c b/fs/namei.c index 9cc91fb7f1565..4e3fc58dae722 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1133,9 +1133,6 @@ static int follow_automount(struct path *path, struct nameidata *nd, path->dentry->d_inode) return -EISDIR; - if (path->dentry->d_sb->s_user_ns != &init_user_ns) - return -EACCES; - nd->total_link_count++; if (nd->total_link_count >= 40) return -ELOOP;