Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit a5ecbcb8 authored by Eric Paris's avatar Eric Paris Committed by James Morris
Browse files

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: default avatarEric Paris <eparis@redhat.com>
Signed-off-by: default avatarJames Morris <jmorris@namei.org>
parent 551e4fb2

security/Kconfig

+18 −0
Original line number Original line Diff line number Diff line
@@ -104,6 +104,24 @@ config SECURITY_ROOTPLUG 
	  

	  

	  If you are unsure how to answer this question, answer N.

	  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/selinux/Kconfig

source security/smack/Kconfig

source security/smack/Kconfig

security/security.c

+3 −1
Original line number Original line Diff line number Diff line
@@ -23,7 +23,9 @@ extern struct security_operations dummy_security_ops; 
extern void security_fixup_ops(struct security_operations *ops);

extern void security_fixup_ops(struct security_operations *ops);





struct security_operations *security_ops;	/* Initialized to NULL */

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)

static inline int verify(struct security_operations *ops)

{

{