blob: 6cc56dca487ea012d6ee42da0e955fced97fc20d [file] [log] [blame]
From 50b96d63dc09c91fac9b33cf3b66bb1c8b899cae Mon Sep 17 00:00:00 2001
From: Andrew Donnellan <>
Date: Tue, 10 Dec 2019 00:22:21 +1100
Subject: [PATCH] powerpc: Fix __clear_user() with KUAP enabled
commit 61e3acd8c693a14fc69b824cb5b08d02cb90a6e7 upstream.
The KUAP implementation adds calls in clear_user() to enable and
disable access to userspace memory. However, it doesn't add these to
__clear_user(), which is used in the ptrace regset code.
As there's only one direct user of __clear_user() (the regset code),
and the time taken to set the AMR for KUAP purposes is going to
dominate the cost of a quick access_ok(), there's not much point
having a separate path.
Rename __clear_user() to __arch_clear_user(), and make __clear_user()
just call clear_user().
Reported-by: Daniel Axtens <>
Suggested-by: Michael Ellerman <>
Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection")
Signed-off-by: Andrew Donnellan <>
[mpe: Use __arch_clear_user() for the asm version like arm64 & nds32]
Signed-off-by: Michael Ellerman <>
Signed-off-by: Paul Gortmaker <>
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 8b03eb44e876..f2d3c29185fd 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -387,7 +387,7 @@ static inline unsigned long raw_copy_to_user(void __user *to,
return ret;
-extern unsigned long __clear_user(void __user *addr, unsigned long size);
+unsigned long __arch_clear_user(void __user *addr, unsigned long size);
static inline unsigned long clear_user(void __user *addr, unsigned long size)
@@ -395,12 +395,17 @@ static inline unsigned long clear_user(void __user *addr, unsigned long size)
if (likely(access_ok(addr, size))) {
allow_write_to_user(addr, size);
- ret = __clear_user(addr, size);
+ ret = __arch_clear_user(addr, size);
prevent_write_to_user(addr, size);
return ret;
+static inline unsigned long __clear_user(void __user *addr, unsigned long size)
+ return clear_user(addr, size);
extern long strncpy_from_user(char *dst, const char __user *src, long count);
extern __must_check long strnlen_user(const char __user *str, long n);
diff --git a/arch/powerpc/lib/string_32.S b/arch/powerpc/lib/string_32.S
index f69a6aab7bfb..1ddb26394e8a 100644
--- a/arch/powerpc/lib/string_32.S
+++ b/arch/powerpc/lib/string_32.S
@@ -17,7 +17,7 @@ CACHELINE_BYTES = L1_CACHE_BYTES
* Use dcbz on the complete cache lines in the destination
* to set them to zero. This requires that the destination
@@ -87,4 +87,4 @@ _GLOBAL(__clear_user)
EX_TABLE(8b, 91b)
EX_TABLE(9b, 91b)
diff --git a/arch/powerpc/lib/string_64.S b/arch/powerpc/lib/string_64.S
index 507b18b1660e..169872bc0892 100644
--- a/arch/powerpc/lib/string_64.S
+++ b/arch/powerpc/lib/string_64.S
@@ -17,7 +17,7 @@ PPC64_CACHES:
.section ".text"
- * __clear_user: - Zero a block of memory in user space, with less checking.
+ * __arch_clear_user: - Zero a block of memory in user space, with less checking.
* @to: Destination address, in user space.
* @n: Number of bytes to zero.
@@ -58,7 +58,7 @@ err3; stb r0,0(r3)
mr r3,r4
cmpdi r4,32
neg r6,r3
li r0,0
@@ -181,4 +181,4 @@ err1; dcbz 0,r3
cmpdi r4,32
blt .Lshort_clear
b .Lmedium_clear