[PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

Christophe Leroy
2021-10-14T05:50:00Z

Behind its location, lkdtm_EXEC_RODATA() executes
lkdtm_rodata_do_nothing() which is a real function,
not a copy of do_nothing().

So executes it directly instead of using execute_location().

This is necessary because following patch will fix execute_location()
to use a copy of the function descriptor of do_nothing() and
function descriptor of lkdtm_rodata_do_nothing() might be different.

And fix displayed addresses by dereferencing the function descriptors.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
drivers/misc/lkdtm/perms.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 035fcca441f0..5266dc28df6e 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -153,7 +153,14 @@ void lkdtm_EXEC_VMALLOC(void)

void lkdtm_EXEC_RODATA(void)
{
- execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
+ pr_info("attempting ok execution at %px\n",
+ dereference_function_descriptor(do_nothing));
+ do_nothing();
+
+ pr_info("attempting bad execution at %px\n",
+ dereference_function_descriptor(lkdtm_rodata_do_nothing));
+ lkdtm_rodata_do_nothing();
+ pr_err("FAIL: func returned\n");
}

void lkdtm_EXEC_USERSPACE(void)
--
2.31.1