As found by [email protected], current -git, when compiled with
CONFIG_USER_NS=n, can be crashed by doing
#include <sched.h>
#include <sys/types.h>
#include <unistd.h>
int main()
{
unshare(CLONE_NEWNS);
setuid(1000);
}
as root.
The dummy version of copy_user_ns was returning NULL instead of
a valid namespace. The following patch fixes the problem.
Please apply.
thanks,
-serge
>From 32f86740d27ef77160e438cd7dc4fcd5df159dd0 Mon Sep 17 00:00:00 2001
From: Serge E. Hallyn <[email protected]>
Date: Tue, 17 Jul 2007 15:28:17 -0400
Subject: [PATCH] user namespace: fix copy_user_ns return value
When a CONFIG_USER_NS=n and a user tries to unshare some
namespace other than the user namespace, the dummy
copy_user_ns returns NULL rather than the old_ns. This
value then gets assigned to task->nsproxy->user_ns, so
that a subsequent setuid, which uses task->nsproxy->user_ns,
causes a NULL pointer deref.
Fix this by returning old_ns.
Signed-off-by: Serge E. Hallyn <[email protected]>
---
include/linux/user_namespace.h | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index bb32057..1101b0c 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -49,7 +49,7 @@ static inline struct user_namespace *copy_user_ns(int flags,
if (flags & CLONE_NEWUSER)
return ERR_PTR(-EINVAL);
- return NULL;
+ return old_ns;
}
static inline void put_user_ns(struct user_namespace *ns)
--
1.5.1.1.GIT
-
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