From e0a94c2a63f2644826069044649669b5e7ca75d3 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 From: Christoph Lameter 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 --- include/linux/mm.h | 2 -- include/linux/security.h | 2 ++ kernel/sysctl.c | 2 -- mm/Kconfig | 19 +++++++++++++++++++ mm/mmap.c | 3 +++ security/Kconfig | 22 +--------------------- security/security.c | 3 --- 7 files changed, 25 insertions(+), 28 deletions(-) --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -580,12 +580,10 @@ static inline void set_page_links(struct */ static inline unsigned long round_hint_to_min(unsigned long hint) { -#ifdef CONFIG_SECURITY hint &= PAGE_MASK; if (((void *)hint != NULL) && (hint < mmap_min_addr)) return PAGE_ALIGN(mmap_min_addr); -#endif return hint; } --- a/include/linux/security.h +++ b/include/linux/security.h @@ -2197,6 +2197,8 @@ static inline int security_file_mmap(str unsigned long addr, unsigned long addr_only) { + if ((addr < mmap_min_addr) && !capable(CAP_SYS_RAWIO)) + return -EACCES; return 0; } --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1225,7 +1225,6 @@ static struct ctl_table vm_table[] = { .strategy = &sysctl_jiffies, }, #endif -#ifdef CONFIG_SECURITY { .ctl_name = CTL_UNNUMBERED, .procname = "mmap_min_addr", @@ -1234,7 +1233,6 @@ static struct ctl_table vm_table[] = { .mode = 0644, .proc_handler = &proc_doulongvec_minmax, }, -#endif #ifdef CONFIG_NUMA { .ctl_name = CTL_UNNUMBERED, --- a/mm/Kconfig +++ b/mm/Kconfig @@ -216,3 +216,21 @@ 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. --- a/mm/mmap.c +++ b/mm/mmap.c @@ -87,6 +87,9 @@ int sysctl_overcommit_ratio = 50; /* def int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT; struct percpu_counter vm_committed_as; +/* 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 --- a/security/Kconfig +++ b/security/Kconfig @@ -110,28 +110,8 @@ config SECURITY_ROOTPLUG See for more information about this module. - - If you are unsure how to answer this question, answer N. - -config SECURITY_DEFAULT_MMAP_MIN_ADDR - int "Low address space to protect from user allocation" - depends on SECURITY - default 0 - 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. + If you are unsure how to answer this question, answer N. source security/selinux/Kconfig source security/smack/Kconfig --- a/security/security.c +++ b/security/security.c @@ -26,9 +26,6 @@ extern void security_fixup_ops(struct se struct security_operations *security_ops; /* Initialized to NULL */ -/* amount of vm to protect from userspace access */ -unsigned long mmap_min_addr = CONFIG_SECURITY_DEFAULT_MMAP_MIN_ADDR; - static inline int verify(struct security_operations *ops) { /* verify the security_operations structure exists */