Re: [PATCH v2 10/10] powerpc/32s: Implement Kernel Userspace Access Protection
From: Christophe Leroy
Date: Tue Apr 23 2019 - 05:26:45 EST
Le 18/04/2019 Ã 08:55, Michael Ellerman a ÃcritÂ:
Christophe Leroy <christophe.leroy@xxxxxx> writes:
diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h
index 5f97c742ca71..b3560b2de435 100644
--- a/arch/powerpc/include/asm/book3s/32/kup.h
+++ b/arch/powerpc/include/asm/book3s/32/kup.h
@@ -37,6 +37,113 @@
...
+
+static inline void allow_user_access(void __user *to, const void __user *from, u32 size)
+{
+ u32 addr = (__force u32)to;
+ u32 end = min(addr + size, TASK_SIZE);
+
+ if (!addr || addr >= TASK_SIZE || !size)
+ return;
+
+ current->thread.kuap = (addr & 0xf0000000) | ((((end - 1) >> 28) + 1) & 0xf);
+ kuap_update_sr(mfsrin(addr) & ~SR_KS, addr, end); /* Clear Ks */
+}
When rebasing on my v6 I changed the above to:
static inline void allow_user_access(void __user *to, const void __user *from, u32 size)
{
u32 addr, end;
if (__builtin_constant_p(to) && to == NULL)
return;
Good point, it avoids keeping the test compiled in when the 'to' is not
NULL.
addr = (__force u32)to;
if (!addr || addr >= TASK_SIZE || !size)
return;
Then the !addr test isn't needed anymore I think.
Christophe
end = min(addr + size, TASK_SIZE);
current->thread.kuap = (addr & 0xf0000000) | ((((end - 1) >> 28) + 1) & 0xf);
kuap_update_sr(mfsrin(addr) & ~SR_KS, addr, end); /* Clear Ks */
}
Which I think achieves the same result. It does boot :)
+
+static inline void prevent_user_access(void __user *to, const void __user *from, u32 size)
+{
+ u32 addr = (__force u32)to;
+ u32 end = min(addr + size, TASK_SIZE);
+
+ if (!addr || addr >= TASK_SIZE || !size)
+ return;
+
+ current->thread.kuap = 0;
+ kuap_update_sr(mfsrin(addr) | SR_KS, addr, end); /* set Ks */
+}
+
+static inline void allow_read_from_user(const void __user *from, unsigned long size)
+{
+}
And I dropped that.
cheers