Backported to 2.6.28 by Kerin Millar Date: Wed, 3 Jun 2009 20:04:31 +0000 (-0400) Subject: security: use mmap_min_addr indepedently of security models X-Git-Tag: v2.6.31-rc1~395^2^2~6 X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=e0a94c2a6 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 Acked-by: Eric Paris Looks-ok-by: Linus Torvalds Signed-off-by: James Morris --- diff -urp a/include/linux/mm.h b/include/linux/mm.h --- a/include/linux/mm.h 2009-07-24 21:37:08.799857560 +0100 +++ b/include/linux/mm.h 2009-07-24 23:13:59.262857283 +0100 @@ -571,12 +571,10 @@ 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; } diff -urp a/include/linux/security.h b/include/linux/security.h --- a/include/linux/security.h 2008-12-24 23:26:37.000000000 +0000 +++ b/include/linux/security.h 2009-07-24 23:13:59.262857283 +0100 @@ -2139,6 +2139,8 @@ 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; } diff -urp a/kernel/sysctl.c b/kernel/sysctl.c --- a/kernel/sysctl.c 2009-07-24 21:37:06.642857660 +0100 +++ b/kernel/sysctl.c 2009-07-24 23:13:59.274857385 +0100 @@ -1138,7 +1138,6 @@ static struct ctl_table vm_table[] = { .strategy = &sysctl_jiffies, }, #endif -#ifdef CONFIG_SECURITY { .ctl_name = CTL_UNNUMBERED, .procname = "mmap_min_addr", @@ -1147,7 +1146,6 @@ static struct ctl_table vm_table[] = { .mode = 0644, .proc_handler = &proc_doulongvec_minmax, }, -#endif #ifdef CONFIG_NUMA { .ctl_name = CTL_UNNUMBERED, diff -urp a/mm/Kconfig b/mm/Kconfig --- a/mm/Kconfig 2008-12-24 23:26:37.000000000 +0000 +++ b/mm/Kconfig 2009-07-24 23:15:16.784588221 +0100 @@ -222,3 +222,22 @@ config UNEVICTABLE_LRU 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 -urp a/mm/mmap.c b/mm/mmap.c --- a/mm/mmap.c 2009-07-24 21:37:09.510857650 +0100 +++ b/mm/mmap.c 2009-07-24 23:13:59.283857547 +0100 @@ -86,6 +86,9 @@ int sysctl_overcommit_ratio = 50; /* def 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 diff -urp a/security/Kconfig b/security/Kconfig --- a/security/Kconfig 2008-12-24 23:26:37.000000000 +0000 +++ b/security/Kconfig 2009-07-24 23:13:59.287857521 +0100 @@ -100,28 +100,8 @@ 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 diff -urp a/security/security.c b/security/security.c --- a/security/security.c 2008-12-24 23:26:37.000000000 +0000 +++ b/security/security.c 2009-07-24 23:13:59.291857543 +0100 @@ -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 */