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-rw-r--r--Documentation/sysctl/vm.txt15
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 1d192565e182..8cfca173d4bc 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -31,6 +31,7 @@ Currently, these files are in /proc/sys/vm:
- min_unmapped_ratio
- min_slab_ratio
- panic_on_oom
+- mmap_min_address
==============================================================
@@ -216,3 +217,17 @@ above-mentioned.
The default value is 0.
1 and 2 are for failover of clustering. Please select either
according to your policy of failover.
+
+==============================================================
+
+mmap_min_addr
+
+This file indicates the amount of address space which a user process will
+be restricted from mmaping. Since kernel null dereference bugs could
+accidentally operate based on the information in the first couple of pages
+of memory userspace processes should not be allowed to write to them. By
+default this value is set to 0 and no protections will be enforced by the
+security module. Setting this value to something like 64k will allow the
+vast majority of applications to work correctly and provide defense in depth
+against future potential kernel bugs.
+