1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
|
From 7d6be33efa0392d41b35a1393a49cacaf68ddd4f Mon Sep 17 00:00:00 2001
From: "Anthony G. Basile" <blueness@gentoo.org>
Date: Sun, 10 Jan 2016 12:18:55 -0500
Subject: [PATCH 09/20] This patch adds support for a restricted
user-controlled namespace on tmpfs filesystem used to house PaX flags. The
namespace must be of the form user.pax.* and its value cannot exceed a size
of 8 bytes.
This is needed even on all Gentoo systems so that XATTR_PAX flags
are preserved for users who might build packages using portage on
a tmpfs system with a non-hardened kernel and then switch to a
hardened kernel with XATTR_PAX enabled.
The namespace is added to any user with Extended Attribute support
enabled for tmpfs. Users who do not enable xattrs will not have
the XATTR_PAX flags preserved.
---
include/uapi/linux/xattr.h | 4 ++++
mm/shmem.c | 7 +++++++
2 files changed, 11 insertions(+)
diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h
index 1590c49cae57..5eab4629a524 100644
--- a/include/uapi/linux/xattr.h
+++ b/include/uapi/linux/xattr.h
@@ -73,5 +73,9 @@
#define XATTR_POSIX_ACL_DEFAULT "posix_acl_default"
#define XATTR_NAME_POSIX_ACL_DEFAULT XATTR_SYSTEM_PREFIX XATTR_POSIX_ACL_DEFAULT
+/* User namespace */
+#define XATTR_PAX_PREFIX XATTR_USER_PREFIX "pax."
+#define XATTR_PAX_FLAGS_SUFFIX "flags"
+#define XATTR_NAME_PAX_FLAGS XATTR_PAX_PREFIX XATTR_PAX_FLAGS_SUFFIX
#endif /* _UAPI_LINUX_XATTR_H */
diff --git a/mm/shmem.c b/mm/shmem.c
index f11aec40f2e1..7b4f54fd1701 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2570,6 +2570,7 @@ static const struct xattr_handler *shmem_xattr_handlers[] = {
static int shmem_xattr_validate(const char *name)
{
struct { const char *prefix; size_t len; } arr[] = {
+ { XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN},
{ XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
{ XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
};
@@ -2625,6 +2626,12 @@ static int shmem_setxattr(struct dentry *dentry, const char *name,
if (err)
return err;
+ if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
+ if (strcmp(name, XATTR_NAME_PAX_FLAGS))
+ return -EOPNOTSUPP;
+ if (size > 8)
+ return -EINVAL;
+ }
return simple_xattr_set(&info->xattrs, name, value, size, flags);
}
|
