From ef296729b735e083d8919e76ac213b8ff237eb78 Mon Sep 17 00:00:00 2001 From: Russell Currey Date: Thu, 18 Apr 2019 16:51:23 +1000 Subject: [PATCH] powerpc/lib: Refactor __patch_instruction() to use __put_user_asm() __patch_instruction() is called in early boot, and uses __put_user_size(), which includes the allow/prevent calls to enforce KUAP, which could either be called too early, or in the Radix case, forced to use "early_" versions of functions just to safely handle this one case. __put_user_asm() does not do this, and thus is safe to use both in early boot, and later on since in this case it should only ever be touching kernel memory. __patch_instruction() was previously refactored to use __put_user_size() in order to be able to return -EFAULT, which would allow the kernel to patch instructions in userspace, which should never happen. This has the functional change of causing faults on userspace addresses if KUAP is turned on, which should never happen in practice. A future enhancement could be to double check the patch address is definitely allowed to be tampered with by the kernel. Signed-off-by: Russell Currey Signed-off-by: Michael Ellerman --- arch/powerpc/lib/code-patching.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c index 587ff9788ab0..90c9d4a1e36f 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -25,9 +25,9 @@ static int __patch_instruction(unsigned int *exec_addr, unsigned int instr, unsigned int *patch_addr) { - int err; + int err = 0; - __put_user_size(instr, patch_addr, 4, err); + __put_user_asm(instr, patch_addr, err, "stw"); if (err) return err;