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authorChristoph Lameter <cl@linux-foundation.org>2009-06-03 16:04:31 -0400
committerJames Morris <jmorris@namei.org>2009-06-04 12:07:48 +1000
commite0a94c2a63f2644826069044649669b5e7ca75d3 (patch)
treedebf8a9af6ac23dadd116dc1cd1f9dcefe9629c6 /mm/Kconfig
parent7d2948b1248109dbc7f4aaf9867c54b1912d494c (diff)
downloadconfigs-e0a94c2a63f2644826069044649669b5e7ca75d3.tar.gz
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>
Diffstat (limited to 'mm/Kconfig')
-rw-r--r--mm/Kconfig19
1 files changed, 19 insertions, 0 deletions
diff --git a/mm/Kconfig b/mm/Kconfig
index c2b57d81e15..71830ba7b98 100644
--- 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