From: Seth Forshee <[email protected]> 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: [email protected] Cc: [email protected] Cc: "Eric W. Biederman" <[email protected]> Cc: Serge Hallyn <[email protected]> Cc: Miklos Szeredi <[email protected]> Acked-by: Miklos Szeredi <[email protected]> Reviewed-by: Serge Hallyn <[email protected]> Reviewed-by: "Eric W. Biederman" <[email protected]> Signed-off-by: Seth Forshee <[email protected]> Signed-off-by: Dongsu Park <[email protected]> Signed-off-by: Eric W. Biederman <[email protected]> --- 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 ad1cfac1942f..d41559a0aa6b 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
