powerpc/book3s64/kup: Check max key supported before enabling kup
Don't enable KUEP/KUAP if we support less than or equal to 3 keys.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201202043854.76406-1-aneesh.kumar@linux.ibm.com
diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h
index 952be04..f8ec679 100644
--- a/arch/powerpc/include/asm/kup.h
+++ b/arch/powerpc/include/asm/kup.h
@@ -44,6 +44,9 @@
#else /* !__ASSEMBLY__ */
+extern bool disable_kuep;
+extern bool disable_kuap;
+
#include <linux/pgtable.h>
void setup_kup(void);
diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
index 4a3aedd..2b7ded3 100644
--- a/arch/powerpc/mm/book3s64/pkeys.c
+++ b/arch/powerpc/mm/book3s64/pkeys.c
@@ -185,6 +185,27 @@ void __init pkey_early_init_devtree(void)
default_uamor &= ~(0x3ul << pkeyshift(execute_only_key));
}
+ if (unlikely(num_pkey <= 3)) {
+ /*
+ * Insufficient number of keys to support
+ * KUAP/KUEP feature.
+ */
+ disable_kuep = true;
+ disable_kuap = true;
+ WARN(1, "Disabling kernel user protection due to low (%d) max supported keys\n", num_pkey);
+ } else {
+ /* handle key which is used by kernel for KAUP */
+ reserved_allocation_mask |= (0x1 << 3);
+ /*
+ * Mark access for kup_key in default amr so that
+ * we continue to operate with that AMR in
+ * copy_to/from_user().
+ */
+ default_amr &= ~(0x3ul << pkeyshift(3));
+ default_iamr &= ~(0x1ul << pkeyshift(3));
+ default_uamor &= ~(0x3ul << pkeyshift(3));
+ }
+
/*
* Allow access for only key 0. And prevent any other modification.
*/
@@ -205,18 +226,6 @@ void __init pkey_early_init_devtree(void)
reserved_allocation_mask |= (0x1 << 1);
default_uamor &= ~(0x3ul << pkeyshift(1));
- /* handle key which is used by kernel for KAUP */
- reserved_allocation_mask |= (0x1 << 3);
- /*
- * Mark access for KUAP key in default amr so that
- * we continue to operate with that AMR in
- * copy_to/from_user().
- */
- default_amr &= ~(0x3ul << pkeyshift(3));
- default_iamr &= ~(0x1ul << pkeyshift(3));
- default_uamor &= ~(0x3ul << pkeyshift(3));
-
-
/*
* Prevent the usage of OS reserved keys. Update UAMOR
* for those keys. Also mark the rest of the bits in the
diff --git a/arch/powerpc/mm/init-common.c b/arch/powerpc/mm/init-common.c
index 8e0d792..afdebb9 100644
--- a/arch/powerpc/mm/init-common.c
+++ b/arch/powerpc/mm/init-common.c
@@ -28,8 +28,8 @@ EXPORT_SYMBOL_GPL(kernstart_addr);
unsigned long kernstart_virt_addr __ro_after_init = KERNELBASE;
EXPORT_SYMBOL_GPL(kernstart_virt_addr);
-static bool disable_kuep = !IS_ENABLED(CONFIG_PPC_KUEP);
-static bool disable_kuap = !IS_ENABLED(CONFIG_PPC_KUAP);
+bool disable_kuep = !IS_ENABLED(CONFIG_PPC_KUEP);
+bool disable_kuap = !IS_ENABLED(CONFIG_PPC_KUAP);
static int __init parse_nosmep(char *p)
{
