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authordcashman <dcashman@google.com>2015-10-02 12:52:57 -0700
committerMark Salyzyn <salyzyn@google.com>2015-10-28 14:31:17 +0000
commit565ef50330f97868b8d01b78c7809e453679ba76 (patch)
treed2ae195b5e03750ba685a8430f86e0fcdc1f3bbd /Documentation/sysctl/kernel.txt
parent70f767ae180a8b7ab0058145ed5375bc357a39a6 (diff)
downloadlinux-linaro-stable-565ef50330f97868b8d01b78c7809e453679ba76.tar.gz
mm: mmap: Add new /proc tunable for mmap_base ASLR.
ASLR currently only uses 8 bits to generate the random offset for the mmap base address on 32 bit architectures. This value was chosen to prevent a poorly chosen value from dividing the address space in such a way as to prevent large allocations. This may not be an issue on all platforms. Allow the specification of a minimum number of bits so that platforms desiring greater ASLR protection may determine where to place the trade-off. BUG=24047224 Signed-off-by: Daniel Cashman <dcashman@google.com> Change-Id: I0aa8f1e416fec848b6817ab861610d8f0eb3beb8
Diffstat (limited to 'Documentation/sysctl/kernel.txt')
-rw-r--r--Documentation/sysctl/kernel.txt14
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 57baff5bdb80..62044945a118 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -41,6 +41,7 @@ show up in /proc/sys/kernel:
- kptr_restrict
- kstack_depth_to_print [ X86 only ]
- l2cr [ PPC only ]
+- mmap_rnd_bits
- modprobe ==> Documentation/debugging-modules.txt
- modules_disabled
- msg_next_id [ sysv ipc ]
@@ -386,6 +387,19 @@ This flag controls the L2 cache of G3 processor boards. If
==============================================================
+mmap_rnd_bits:
+
+This value can be used to select the number of bits to use to
+determine the random offset to the base address of vma regions
+resulting from mmap allocations on architectures which support
+tuning address space randomization. This value will be bounded
+by the architecture's minimum and maximum supported values.
+
+This value can be changed after boot using the
+/proc/sys/kernel/mmap_rnd_bits tunable
+
+==============================================================
+
modules_disabled:
A toggle value indicating if modules are allowed to be loaded