[PATCH v4 10/17] lkdtm: use function_nocfi
From: Sami Tolvanen <samitolvanen@google.com>
Date: 2021-03-31 21:29:25
Also in:
linux-arch, linux-arm-kernel, linux-hardening, linux-kbuild, linux-pci, lkml
Subsystem:
char and misc drivers, linux kernel dump test module (lkdtm), the rest · Maintainers:
Arnd Bergmann, Greg Kroah-Hartman, Kees Cook, Linus Torvalds
To ensure we take the actual address of a function in kernel text, use function_nocfi. 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 <redacted> --- 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..15d220ef35a5 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, function_nocfi(vm_mmap), unconst + PAGE_SIZE)) { pr_warn("copy_to_user failed, but lacked Oops\n"); goto free_user;
--
2.31.0.291.g576ba9dcdaf-goog