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authorEric Paris <eparis@redhat.com>2007-06-28 15:55:21 -0400
committerJames Morris <jmorris@namei.org>2007-07-11 22:52:29 -0400
commited0321895182ffb6ecf210e066d87911b270d587 (patch)
tree832bb54666f73b06e55322df40f915c5e9ef64d7 /security
parent13bddc2e9d591e31bf20020dc19ea6ca85de420e (diff)
downloadlinux-linaro-ed0321895182ffb6ecf210e066d87911b270d587.tar.gz
security: Protection for exploiting null dereference using mmap
Add a new security check on mmap operations to see if the user is attempting to mmap to low area of the address space. The amount of space protected is indicated by the new proc tunable /proc/sys/vm/mmap_min_addr and defaults to 0, preserving existing behavior. This patch uses a new SELinux security class "memprotect." Policy already contains a number of allow rules like a_t self:process * (unconfined_t being one of them) which mean that putting this check in the process class (its best current fit) would make it useless as all user processes, which we also want to protect against, would be allowed. By taking the memprotect name of the new class it will also make it possible for us to move some of the other memory protect permissions out of 'process' and into the new class next time we bump the policy version number (which I also think is a good future idea) Acked-by: Stephen Smalley <sds@tycho.nsa.gov> Acked-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Eric Paris <eparis@redhat.com> Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'security')
-rw-r--r--security/dummy.c6
-rw-r--r--security/security.c2
-rw-r--r--security/selinux/hooks.c12
-rw-r--r--security/selinux/include/av_perm_to_string.h1
-rw-r--r--security/selinux/include/av_permissions.h1
-rw-r--r--security/selinux/include/class_to_string.h1
-rw-r--r--security/selinux/include/flask.h1
7 files changed, 19 insertions, 5 deletions
diff --git a/security/dummy.c b/security/dummy.c
index 8ffd76405b5..d6a112ce297 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -420,8 +420,12 @@ static int dummy_file_ioctl (struct file *file, unsigned int command,
static int dummy_file_mmap (struct file *file, unsigned long reqprot,
unsigned long prot,
- unsigned long flags)
+ unsigned long flags,
+ unsigned long addr,
+ unsigned long addr_only)
{
+ if (addr < mmap_min_addr)
+ return -EACCES;
return 0;
}
diff --git a/security/security.c b/security/security.c
index fc8601b2b7a..024484fc59b 100644
--- a/security/security.c
+++ b/security/security.c
@@ -24,6 +24,7 @@ extern struct security_operations dummy_security_ops;
extern void security_fixup_ops(struct security_operations *ops);
struct security_operations *security_ops; /* Initialized to NULL */
+unsigned long mmap_min_addr; /* 0 means no protection */
static inline int verify(struct security_operations *ops)
{
@@ -176,4 +177,5 @@ EXPORT_SYMBOL_GPL(register_security);
EXPORT_SYMBOL_GPL(unregister_security);
EXPORT_SYMBOL_GPL(mod_reg_security);
EXPORT_SYMBOL_GPL(mod_unreg_security);
+EXPORT_SYMBOL_GPL(mmap_min_addr);
EXPORT_SYMBOL(security_ops);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index b29059ecc04..78c3f98fcdc 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2569,12 +2569,16 @@ static int file_map_prot_check(struct file *file, unsigned long prot, int shared
}
static int selinux_file_mmap(struct file *file, unsigned long reqprot,
- unsigned long prot, unsigned long flags)
+ unsigned long prot, unsigned long flags,
+ unsigned long addr, unsigned long addr_only)
{
- int rc;
+ int rc = 0;
+ u32 sid = ((struct task_security_struct*)(current->security))->sid;
- rc = secondary_ops->file_mmap(file, reqprot, prot, flags);
- if (rc)
+ if (addr < mmap_min_addr)
+ rc = avc_has_perm(sid, sid, SECCLASS_MEMPROTECT,
+ MEMPROTECT__MMAP_ZERO, NULL);
+ if (rc || addr_only)
return rc;
if (selinux_checkreqprot)
diff --git a/security/selinux/include/av_perm_to_string.h b/security/selinux/include/av_perm_to_string.h
index b83e74012a9..049bf69429b 100644
--- a/security/selinux/include/av_perm_to_string.h
+++ b/security/selinux/include/av_perm_to_string.h
@@ -158,3 +158,4 @@
S_(SECCLASS_KEY, KEY__CREATE, "create")
S_(SECCLASS_DCCP_SOCKET, DCCP_SOCKET__NODE_BIND, "node_bind")
S_(SECCLASS_DCCP_SOCKET, DCCP_SOCKET__NAME_CONNECT, "name_connect")
+ S_(SECCLASS_MEMPROTECT, MEMPROTECT__MMAP_ZERO, "mmap_zero")
diff --git a/security/selinux/include/av_permissions.h b/security/selinux/include/av_permissions.h
index 5fee1735bff..eda89a2ec63 100644
--- a/security/selinux/include/av_permissions.h
+++ b/security/selinux/include/av_permissions.h
@@ -823,3 +823,4 @@
#define DCCP_SOCKET__NAME_BIND 0x00200000UL
#define DCCP_SOCKET__NODE_BIND 0x00400000UL
#define DCCP_SOCKET__NAME_CONNECT 0x00800000UL
+#define MEMPROTECT__MMAP_ZERO 0x00000001UL
diff --git a/security/selinux/include/class_to_string.h b/security/selinux/include/class_to_string.h
index 37879906844..e77de0e62ea 100644
--- a/security/selinux/include/class_to_string.h
+++ b/security/selinux/include/class_to_string.h
@@ -63,3 +63,4 @@
S_("key")
S_(NULL)
S_("dccp_socket")
+ S_("memprotect")
diff --git a/security/selinux/include/flask.h b/security/selinux/include/flask.h
index 35f309f4787..a9c2b20f14b 100644
--- a/security/selinux/include/flask.h
+++ b/security/selinux/include/flask.h
@@ -49,6 +49,7 @@
#define SECCLASS_PACKET 57
#define SECCLASS_KEY 58
#define SECCLASS_DCCP_SOCKET 60
+#define SECCLASS_MEMPROTECT 61
/*
* Security identifier indices for initial entities