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lkdtm: use function_nocfi

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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 <[email protected]>
Acked-by: Kees Cook <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
This commit is contained in:
Sami Tolvanen authored and Kees Cook committed 2021-04-08 16:04:22 -07:00
1 parent 4f0f586bf0
commit 6c4df54ed2
1 file changed
+1 -1
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drivers/misc/lkdtm/usercopy.c
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@@ -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;