lkml.org 
[lkml]   [2016]   [Dec]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCHv4 09/10] mm/usercopy: Switch to using lm_alias
On Tue, Nov 29, 2016 at 11:39:44AM -0800, Kees Cook wrote:
> On Tue, Nov 29, 2016 at 10:55 AM, Laura Abbott <labbott@redhat.com> wrote:
> >
> > The usercopy checking code currently calls __va(__pa(...)) to check for
> > aliases on symbols. Switch to using lm_alias instead.
> >
> > Signed-off-by: Laura Abbott <labbott@redhat.com>
>
> Acked-by: Kees Cook <keescook@chromium.org>
>
> I should probably add a corresponding alias test to lkdtm...
>
> -Kees

Something like the below?

It uses lm_alias(), so it depends on Laura's patches. We seem to do the
right thing, anyhow:

root@ribbensteg:/home/nanook# echo USERCOPY_KERNEL_ALIAS > /sys/kernel/debug/provoke-crash/DIRECT
[ 44.493400] usercopy: kernel memory exposure attempt detected from ffff80000031a730 (<linear kernel text>) (4096 bytes)
[ 44.504263] kernel BUG at mm/usercopy.c:75!

Thanks,
Mark.

---->8----
diff --git a/drivers/misc/lkdtm.h b/drivers/misc/lkdtm.h
index fdf954c..96d8d76 100644
--- a/drivers/misc/lkdtm.h
+++ b/drivers/misc/lkdtm.h
@@ -56,5 +56,6 @@
void lkdtm_USERCOPY_STACK_FRAME_FROM(void);
void lkdtm_USERCOPY_STACK_BEYOND(void);
void lkdtm_USERCOPY_KERNEL(void);
+void lkdtm_USERCOPY_KERNEL_ALIAS(void);

#endif
diff --git a/drivers/misc/lkdtm_core.c b/drivers/misc/lkdtm_core.c
index f9154b8..f6bc6d6 100644
--- a/drivers/misc/lkdtm_core.c
+++ b/drivers/misc/lkdtm_core.c
@@ -228,6 +228,7 @@ struct crashtype crashtypes[] = {
CRASHTYPE(USERCOPY_STACK_FRAME_FROM),
CRASHTYPE(USERCOPY_STACK_BEYOND),
CRASHTYPE(USERCOPY_KERNEL),
+ CRASHTYPE(USERCOPY_KERNEL_ALIAS),
};


diff --git a/drivers/misc/lkdtm_usercopy.c b/drivers/misc/lkdtm_usercopy.c
index 1dd6114..955f2dc 100644
--- a/drivers/misc/lkdtm_usercopy.c
+++ b/drivers/misc/lkdtm_usercopy.c
@@ -279,9 +279,16 @@ void lkdtm_USERCOPY_STACK_BEYOND(void)
do_usercopy_stack(true, false);
}

-void lkdtm_USERCOPY_KERNEL(void)
+static void do_usercopy_kernel(bool use_alias)
{
unsigned long user_addr;
+ const void *rodata = test_text;
+ void *text = vm_mmap;
+
+ if (use_alias) {
+ rodata = lm_alias(rodata);
+ text = lm_alias(text);
+ }

user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
PROT_READ | PROT_WRITE | PROT_EXEC,
@@ -292,14 +299,14 @@ void lkdtm_USERCOPY_KERNEL(void)
}

pr_info("attempting good copy_to_user from kernel rodata\n");
- if (copy_to_user((void __user *)user_addr, test_text,
+ if (copy_to_user((void __user *)user_addr, rodata,
unconst + sizeof(test_text))) {
pr_warn("copy_to_user failed unexpectedly?!\n");
goto free_user;
}

pr_info("attempting bad copy_to_user from kernel text\n");
- if (copy_to_user((void __user *)user_addr, vm_mmap,
+ if (copy_to_user((void __user *)user_addr, text,
unconst + PAGE_SIZE)) {
pr_warn("copy_to_user failed, but lacked Oops\n");
goto free_user;
@@ -309,6 +316,16 @@ void lkdtm_USERCOPY_KERNEL(void)
vm_munmap(user_addr, PAGE_SIZE);
}

+void lkdtm_USERCOPY_KERNEL(void)
+{
+ do_usercopy_kernel(false);
+}
+
+void lkdtm_USERCOPY_KERNEL_ALIAS(void)
+{
+ do_usercopy_kernel(true);
+}
+
void __init lkdtm_usercopy_init(void)
{
/* Prepare cache that lacks SLAB_USERCOPY flag. */
\
 
 \ /
  Last update: 2016-12-06 19:20    [W:0.102 / U:0.860 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site