Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6

[cascardo/linux.git] / mm / Kconfig

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