40 lines
1.3 KiB
Diff
40 lines
1.3 KiB
Diff
From: "Eric W. Biederman" <ebiederm@xmission.com>
|
|
Date: Fri, 5 Dec 2014 18:26:30 -0600
|
|
Subject: [PATCH] userns: Check euid no fsuid when establishing an unprivileged
|
|
uid mapping
|
|
|
|
setresuid allows the euid to be set to any of uid, euid, suid, and
|
|
fsuid. Therefor it is safe to allow an unprivileged user to map
|
|
their euid and use CAP_SETUID privileged with exactly that uid,
|
|
as no new credentials can be obtained.
|
|
|
|
I can not find a combination of existing system calls that allows setting
|
|
uid, euid, suid, and fsuid from the fsuid making the previous use
|
|
of fsuid for allowing unprivileged mappings a bug.
|
|
|
|
This is part of a fix for CVE-2014-8989.
|
|
|
|
Cc: stable@vger.kernel.org
|
|
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
|
|
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
|
|
---
|
|
kernel/user_namespace.c | 2 +-
|
|
1 file changed, 1 insertion(+), 1 deletion(-)
|
|
|
|
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
|
|
index 1ce6d67c07b7..9451b12a9b6c 100644
|
|
--- a/kernel/user_namespace.c
|
|
+++ b/kernel/user_namespace.c
|
|
@@ -819,7 +819,7 @@ static bool new_idmap_permitted(const struct file *file,
|
|
u32 id = new_map->extent[0].lower_first;
|
|
if (cap_setid == CAP_SETUID) {
|
|
kuid_t uid = make_kuid(ns->parent, id);
|
|
- if (uid_eq(uid, file->f_cred->fsuid))
|
|
+ if (uid_eq(uid, file->f_cred->euid))
|
|
return true;
|
|
}
|
|
}
|
|
--
|
|
2.1.0
|
|
|