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kernel 4.9: backport definition of NS_GET_NSTYPE

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That is required for procd-ujail compilation.
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AmadeusGhost 2021-12-06 23:01:08 +08:00
parent 80783f2a89
commit 3ad4abcb7b
1 changed files with 68 additions and 0 deletions
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target/linux/generic/backport-4.9/050-v4.11-nsfs-Add-an-ioctl-to-return-the-namespace-type.patch Normal file
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@ -0,0 +1,68 @@
From e5ff5ce6e20ee22511398bb31fb912466cf82a36 Mon Sep 17 00:00:00 2001
From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Date: Wed, 25 Jan 2017 14:03:36 +1300
Subject: [PATCH] nsfs: Add an ioctl() to return the namespace type
Linux 4.9 added two ioctl() operations that can be used to discover:
* the parental relationships for hierarchical namespaces (user and PID)
[NS_GET_PARENT]
* the user namespaces that owns a specified non-user-namespace
[NS_GET_USERNS]
For no good reason that I can glean, NS_GET_USERNS was made synonymous
with NS_GET_PARENT for user namespaces. It might have been better if
NS_GET_USERNS had returned an error if the supplied file descriptor
referred to a user namespace, since it suggests that the caller may be
confused. More particularly, if it had generated an error, then I wouldn't
need the new ioctl() operation proposed here. (On the other hand, what
I propose here may be more generally useful.)
I would like to write code that discovers namespace relationships for
the purpose of understanding the namespace setup on a running system.
In particular, given a file descriptor (or pathname) for a namespace,
N, I'd like to obtain the corresponding user namespace. Namespace N
might be a user namespace (in which case my code would just use N) or
a non-user namespace (in which case my code will use NS_GET_USERNS to
get the user namespace associated with N). The problem is that there
is no way to tell the difference by looking at the file descriptor
(and if I try to use NS_GET_USERNS on an N that is a user namespace, I
get the parent user namespace of N, which is not what I want).
This patch therefore adds a new ioctl(), NS_GET_NSTYPE, which, given
a file descriptor that refers to a user namespace, returns the
namespace type (one of the CLONE_NEW* constants).
Signed-off-by: Michael Kerrisk <mtk-manpages@gmail.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
fs/nsfs.c | 2 ++
include/uapi/linux/nsfs.h | 3 +++
2 files changed, 5 insertions(+)
diff --git a/fs/nsfs.c b/fs/nsfs.c
index 8c9fb29c66732..5d534763c6626 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -173,6 +173,8 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
if (!ns->ops->get_parent)
return -EINVAL;
return open_related_ns(ns, ns->ops->get_parent);
+ case NS_GET_NSTYPE:
+ return ns->ops->type;
default:
return -ENOTTY;
}
diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h
index 3af617230d1b7..2b48df11056ac 100644
--- a/include/uapi/linux/nsfs.h
+++ b/include/uapi/linux/nsfs.h
@@ -9,5 +9,8 @@
#define NS_GET_USERNS _IO(NSIO, 0x1)
/* Returns a file descriptor that refers to a parent namespace */
#define NS_GET_PARENT _IO(NSIO, 0x2)
+/* Returns the type of namespace (CLONE_NEW* value) referred to by
+ file descriptor */
+#define NS_GET_NSTYPE _IO(NSIO, 0x3)
#endif /* __LINUX_NSFS_H */