diff mbox series

[10/17] lkdtm: use __va_function

Message ID 20210312004919.669614-11-samitolvanen@google.com (mailing list archive)
State New
Headers show
Series Add support for Clang CFI | expand

Commit Message

Sami Tolvanen March 12, 2021, 12:49 a.m. UTC
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(-)

Comments

Kees Cook March 12, 2021, 2:45 a.m. UTC | #1
On Thu, Mar 11, 2021 at 04:49:12PM -0800, Sami Tolvanen wrote:
> 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>

Acked-by: Kees Cook <keescook@chromium.org>
diff mbox series

Patch

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;