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[PATCH] selinux: add executable stack check

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This patch adds an execstack permission check that controls the ability to
make the main process stack executable so that attempts to make the stack
executable can still be prevented even if the process is allowed the
existing execmem permission in order to e.g.  perform runtime code
generation.  Note that this does not yet address thread stacks.  Note also
that unlike the execmem check, the execstack check is only applied on
mprotect calls, not mmap calls, as the current security_file_mmap hook is
not passed the necessary information presently.

The original author of the code that makes the distinction of the stack
region, is Ingo Molnar, who wrote it within his patch for
/proc/<pid>/maps markers.
(http://marc.theaimsgroup.com/?l=linux-kernel&m=110719881508591&w=2)

The patches also can be found at:
http://pearls.tuxedo-es.org/patches/selinux/policy-execstack.patch
http://pearls.tuxedo-es.org/patches/selinux/kernel-execstack.patch

policy-execstack.patch is the patch that needs to be applied to the policy in
order to support the execstack permission and exclude it
from general_domain_access within macros/core_macros.te.

kernel-execstack.patch adds such permission to the SELinux code within
the kernel and adds the proper permission check to the selinux_file_mprotect() hook.

Signed-off-by: Lorenzo Hernandez Garcia-Hierro <lorenzo@gnu.org>
Acked-by: James Morris <jmorris@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Lorenzo Hernandez Garca-Hierro 2005-06-25 14:54:34 -07:00 committed by Linus Torvalds
parent 2d15cab85b
commit 6b9921976f
3 changed files with 12 additions and 0 deletions
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10
security/selinux/hooks.c
View File

@ -2488,6 +2488,16 @@ static int selinux_file_mprotect(struct vm_area_struct *vma,
if (rc)
return rc;
}
if (!vma->vm_file && (prot & PROT_EXEC) &&
vma->vm_start <= vma->vm_mm->start_stack &&
vma->vm_end >= vma->vm_mm->start_stack) {
/* Attempt to make the process stack executable.
* This has an additional execstack check.
*/
rc = task_has_perm(current, current, PROCESS__EXECSTACK);
if (rc)
return rc;
}
#endif
return file_map_prot_check(vma->vm_file, prot, vma->vm_flags&VM_SHARED);

1
security/selinux/include/av_perm_to_string.h
View File

@ -70,6 +70,7 @@
S_(SECCLASS_PROCESS, PROCESS__DYNTRANSITION, "dyntransition")
S_(SECCLASS_PROCESS, PROCESS__SETCURRENT, "setcurrent")
S_(SECCLASS_PROCESS, PROCESS__EXECMEM, "execmem")
S_(SECCLASS_PROCESS, PROCESS__EXECSTACK, "execstack")
S_(SECCLASS_MSGQ, MSGQ__ENQUEUE, "enqueue")
S_(SECCLASS_MSG, MSG__SEND, "send")
S_(SECCLASS_MSG, MSG__RECEIVE, "receive")

1
security/selinux/include/av_permissions.h
View File

@ -465,6 +465,7 @@
#define PROCESS__DYNTRANSITION 0x00800000UL
#define PROCESS__SETCURRENT 0x01000000UL
#define PROCESS__EXECMEM 0x02000000UL
#define PROCESS__EXECSTACK 0x04000000UL
#define IPC__CREATE 0x00000001UL
#define IPC__DESTROY 0x00000002UL