Messages in this thread Patch in this message | | | From | "Eric W. Biederman" <> | Date | Mon, 26 Feb 2018 17:53:02 -0600 | Subject | [PATCH v7 7/7] fuse: Restrict allow_other to the superblock's namespace or a descendant |
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From: Seth Forshee <seth.forshee@canonical.com>
Unprivileged users are normally restricted from mounting with the allow_other option by system policy, but this could be bypassed for a mount done with user namespace root permissions. In such cases allow_other should not allow users outside the userns to access the mount as doing so would give the unprivileged user the ability to manipulate processes it would otherwise be unable to manipulate. Restrict allow_other to apply to users in the same userns used at mount or a descendant of that namespace. Also export current_in_userns() for use by fuse when built as a module.
Cc: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: Miklos Szeredi <mszeredi@redhat.com> Acked-by: Miklos Szeredi <mszeredi@redhat.com> Reviewed-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: Dongsu Park <dongsu@kinvolk.io> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> --- fs/fuse/dir.c | 2 +- kernel/user_namespace.c | 1 + 2 files changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 79cca1687457..0cbd1ff3dd48 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1030,7 +1030,7 @@ int fuse_allow_current_process(struct fuse_conn *fc) const struct cred *cred; if (fc->allow_other) - return 1; + return current_in_userns(fc->user_ns); cred = current_cred(); if (uid_eq(cred->euid, fc->user_id) && diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 246d4d4ce5c7..492c255e6c5a 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -1235,6 +1235,7 @@ bool current_in_userns(const struct user_namespace *target_ns) { return in_userns(target_ns, current_user_ns()); } +EXPORT_SYMBOL(current_in_userns); static inline struct user_namespace *to_user_ns(struct ns_common *ns) { -- 2.14.1
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