diff options
| author | Eric Paris <eparis@redhat.com> | 2008-01-31 15:11:22 -0500 |
|---|---|---|
| committer | James Morris <jmorris@localhost.localdomain> | 2008-02-06 21:39:46 +0800 |
| commit | a5ecbcb8c13ea8a822d243bf782d0dc9525b4f84 (patch) | |
| tree | 902df830bf581642a49bbb1e4f4de5b9f80eeaa1 | |
| parent | 551e4fb2465b87de9d4aa1669b27d624435443bb (diff) | |
security: allow Kconfig to set default mmap_min_addr protection
Since it was decided that low memory protection from userspace couldn't
be turned on by default add a Kconfig option to allow users/distros to
set a default at compile time. This value is still tunable after boot
in /proc/sys/vm/mmap_min_addr
Discussion:
http://www.mail-archive.com/linux-security-module@vger.kernel.org/msg02543.html
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
| -rw-r--r-- | security/Kconfig | 18 | ||||
| -rw-r--r-- | security/security.c | 4 |
2 files changed, 21 insertions, 1 deletions
diff --git a/security/Kconfig b/security/Kconfig index 25ffe1b9dc9..5dfc206748c 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -104,6 +104,24 @@ config SECURITY_ROOTPLUG 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 users with lots of address space a value of 65536 is + reasonable and should cause no problems. 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. + + source security/selinux/Kconfig source security/smack/Kconfig diff --git a/security/security.c b/security/security.c index b6c57a6b2ff..d15e56cbaad 100644 --- a/security/security.c +++ b/security/security.c @@ -23,7 +23,9 @@ extern struct security_operations dummy_security_ops; extern void security_fixup_ops(struct security_operations *ops); struct security_operations *security_ops; /* Initialized to NULL */ -unsigned long mmap_min_addr; /* 0 means no protection */ + +/* 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) { |