From d6055cd3a734696779d238f9e54174954f22c4c9 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Wed, 3 Jun 2009 16:04:31 -0400 Subject: 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 Acked-by: Eric Paris Looks-ok-by: Linus Torvalds Signed-off-by: James Morris Signed-off-by: Greg Kroah-Hartman --- mm/Kconfig | 18 ++++++++++++++++++ mm/mmap.c | 3 +++ 2 files changed, 21 insertions(+) (limited to 'mm') 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. diff --git a/mm/mmap.c b/mm/mmap.c index 2ae093ed2cac..d330758ccfed 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -86,6 +86,9 @@ int sysctl_overcommit_ratio = 50; /* default is 50% */ int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT; atomic_long_t vm_committed_space = ATOMIC_LONG_INIT(0); +/* amount of vm to protect from userspace access */ +unsigned long mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR; + /* * Check that a process has enough memory to allocate a new virtual * mapping. 0 means there is enough memory for the allocation to -- cgit v1.2.3