[PATCH 10/17] lkdtm: use __va_function

Sami Tolvanen
2021-03-12T00:50:22Z

To ensure we take the actual address of a function in kernel text, use
__va_function. Otherwise, with CONFIG_CFI_CLANG, the compiler replaces
the address with a pointer to the CFI jump table, which is actually in
the module when compiled with CONFIG_LKDTM=m.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
drivers/misc/lkdtm/usercopy.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c
index 109e8d4302c1..d173d6175c87 100644
--- a/drivers/misc/lkdtm/usercopy.c
+++ b/drivers/misc/lkdtm/usercopy.c
@@ -314,7 +314,7 @@ void lkdtm_USERCOPY_KERNEL(void)

pr_info("attempting bad copy_to_user from kernel text: %px\n",
vm_mmap);
- if (copy_to_user((void __user *)user_addr, vm_mmap,
+ if (copy_to_user((void __user *)user_addr, __va_function(vm_mmap),
unconst + PAGE_SIZE)) {
pr_warn("copy_to_user failed, but lacked Oops\n");
goto free_user;
--
2.31.0.rc2.261.g7f71774620-goog