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authorChristoph Lameter <cl@linux-foundation.org>2009-06-03 16:04:31 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2009-07-19 20:44:59 -0700
commitd6055cd3a734696779d238f9e54174954f22c4c9 (patch)
treeb8b99dae159c10c22dd92a77d3f7ad85d40899a1 /mm/Kconfig
parent92e7e4cf8ce653e532aa3cb9857df8316a6b2731 (diff)
security: use mmap_min_addr indepedently of security models
commit e0a94c2a63f2644826069044649669b5e7ca75d3 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'mm/Kconfig')
-rw-r--r--mm/Kconfig18
1 files changed, 18 insertions, 0 deletions
diff --git a/mm/Kconfig b/mm/Kconfig
index 0bd9c2dbb2a0..07b4ec477103 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -208,3 +208,21 @@ config VIRT_TO_BUS
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.