Re: [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()
From: Kees Cook <hidden>
Date: 2021-10-15 21:33:03
Also in:
linux-mm, linuxppc-dev, lkml
On Thu, Oct 14, 2021 at 07:50:00AM +0200, Christophe Leroy wrote:
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 <redacted>
I still don't understand this -- it doesn't look needed at all given the changes in patch 12. (i.e. everything is using dereference_function_descriptor() now) Can't this patch be dropped? -Kees
quoted hunk ↗ jump to hunk
--- 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
-- Kees Cook