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Date: Sat, 3 Mar 2018 22:26:16 +0000 From: Sasha Levin <Alexander.Levin@...rosoft.com> To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "stable@...r.kernel.org" <stable@...r.kernel.org> CC: "Eric W. Biederman" <ebiederm@...ssion.com>, Sasha Levin <Alexander.Levin@...rosoft.com> Subject: [PATCH AUTOSEL for 4.14 28/84] userns: Don't fail follow_automount based on s_user_ns From: "Eric W. Biederman" <ebiederm@...ssion.com> [ 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 <raven@...maw.net> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com> Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com> --- fs/namei.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 62a0db6e6725..cbe24e367a70 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; -- 2.14.1
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