security: use mmap_min_addr indepedently of security models

This patch removes the dependency of mmap_min_addr on CONFIG_SECURITY.
It also sets a default mmap_min_addr of 4096.

mmapping of addresses below 4096 will only be possible for processes
with CAP_SYS_RAWIO.

Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Acked-by: Eric Paris <eparis@redhat.com>
Looks-ok-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: James Morris <jmorris@namei.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index bff1f0d..0c21af6 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -580,12 +580,10 @@ static inline void set_page_links(struct page *page, enum zone_type zone,
  */
 static inline unsigned long round_hint_to_min(unsigned long hint)
 {
-#ifdef CONFIG_SECURITY
        hint &= PAGE_MASK;
        if (((void *)hint != NULL) &&
            (hint < mmap_min_addr))
                return PAGE_ALIGN(mmap_min_addr);
-#endif
        return hint;
 }
 

diff --git a/include/linux/security.h b/include/linux/security.h
index d5fd616..5eff459 100644 (file)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -2197,6 +2197,8 @@ static inline int security_file_mmap(struct file *file, unsigned long reqprot,
                                     unsigned long addr,
                                     unsigned long addr_only)
 {
+       if ((addr < mmap_min_addr) && !capable(CAP_SYS_RAWIO))
+               return -EACCES;
        return 0;
 }
 

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 149581f..45bd711 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1237,7 +1237,6 @@ static struct ctl_table vm_table[] = {
                .strategy       = &sysctl_jiffies,
        },
 #endif
-#ifdef CONFIG_SECURITY
        {
                .ctl_name       = CTL_UNNUMBERED,
                .procname       = "mmap_min_addr",
@@ -1246,7 +1245,6 @@ static struct ctl_table vm_table[] = {
                .mode           = 0644,
                .proc_handler   = &proc_doulongvec_minmax,
        },
-#endif
 #ifdef CONFIG_NUMA
        {
                .ctl_name       = CTL_UNNUMBERED,

diff --git a/mm/Kconfig b/mm/Kconfig
index c2b57d8..71830ba 100644 (file)
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -226,6 +226,25 @@ config HAVE_MLOCKED_PAGE_BIT
 config MMU_NOTIFIER
        bool
 
+config DEFAULT_MMAP_MIN_ADDR
+        int "Low address space to protect from user allocation"
+        default 4096
+        help
+         This is the portion of low virtual memory which should be protected
+         from userspace allocation.  Keeping a user from writing to low pages
+         can help reduce the impact of kernel NULL pointer bugs.
+
+         For most ia64, ppc64 and x86 users with lots of address space
+         a value of 65536 is reasonable and should cause no problems.
+         On arm and other archs it should not be higher than 32768.
+         Programs which use vm86 functionality would either need additional
+         permissions from either the LSM or the capabilities module or have
+         this protection disabled.
+
+         This value can be changed after boot using the
+         /proc/sys/vm/mmap_min_addr tunable.
+
+
 config NOMMU_INITIAL_TRIM_EXCESS
        int "Turn on mmap() excess space trimming before booting"
        depends on !MMU

diff --git a/mm/mmap.c b/mm/mmap.c
index 6b7b1a9..2b43fa1 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -87,6 +87,9 @@ int sysctl_overcommit_ratio = 50;     /* default is 50% */
 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
 struct percpu_counter vm_committed_as;
 
+/* amount of vm to protect from userspace access */
+unsigned long mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
+
 /*
  * Check that a process has enough memory to allocate a new virtual
  * mapping. 0 means there is enough memory for the allocation to

diff --git a/security/Kconfig b/security/Kconfig
index bb24477..d23c839 100644 (file)
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -110,28 +110,8 @@ config SECURITY_ROOTPLUG
 
          See <http://www.linuxjournal.com/article.php?sid=6279> for
          more information about this module.
-         
-         If you are unsure how to answer this question, answer N.
-
-config SECURITY_DEFAULT_MMAP_MIN_ADDR
-        int "Low address space to protect from user allocation"
-        depends on SECURITY
-        default 0
-        help
-         This is the portion of low virtual memory which should be protected
-         from userspace allocation.  Keeping a user from writing to low pages
-         can help reduce the impact of kernel NULL pointer bugs.
-
-         For most ia64, ppc64 and x86 users with lots of address space
-         a value of 65536 is reasonable and should cause no problems.
-         On arm and other archs it should not be higher than 32768.
-         Programs which use vm86 functionality would either need additional
-         permissions from either the LSM or the capabilities module or have
-         this protection disabled.
-
-         This value can be changed after boot using the
-         /proc/sys/vm/mmap_min_addr tunable.
 
+         If you are unsure how to answer this question, answer N.
 
 source security/selinux/Kconfig
 source security/smack/Kconfig

diff --git a/security/security.c b/security/security.c
index 5284255..dc7674f 100644 (file)
--- a/security/security.c
+++ b/security/security.c
@@ -26,9 +26,6 @@ extern void security_fixup_ops(struct security_operations *ops);
 
 struct security_operations *security_ops;      /* Initialized to NULL */
 
-/* amount of vm to protect from userspace access */
-unsigned long mmap_min_addr = CONFIG_SECURITY_DEFAULT_MMAP_MIN_ADDR;
-
 static inline int verify(struct security_operations *ops)
 {
        /* verify the security_operations structure exists */