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(), 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 clear_user_asm(), and make __clear_user() just
call clear_user().
Reported-by: syzbot+f25ecf4b2982d8c7a...@syzkaller-ppc64.appspotmail.com
Reported-by: Daniel Axtens <d...@axtens.net>
Suggested-by: Michael Ellerman <m...@ellerman.id.au>
Cc: Christophe Leroy <christophe.le...@c-s.fr>
Cc: Russell Currey <rus...@russell.cc>
Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access
Protection")
Signed-off-by: Andrew Donnellan <a...@linux.ibm.com>
---
arch/powerpc/include/asm/uaccess.h | 9 +++++++--
arch/powerpc/lib/string_32.S | 4 ++--
arch/powerpc/lib/string_64.S | 6 +++---
3 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/include/asm/uaccess.h
b/arch/powerpc/include/asm/uaccess.h
index 15002b51ff18..d05bc0a4cafa 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -401,7 +401,7 @@ copy_to_user_mcsafe(void __user *to, const void *from,
unsigned long n)
return n;
}
-extern unsigned long __clear_user(void __user *addr, unsigned long size);
+extern unsigned long clear_user_asm(void __user *addr, unsigned long size);
static inline unsigned long clear_user(void __user *addr, unsigned long size)
{
@@ -409,12 +409,17 @@ static inline unsigned long clear_user(void __user *addr,
unsigned long size)
might_fault();
if (likely(access_ok(addr, size))) {
allow_write_to_user(addr, size);
- ret = __clear_user(addr, size);
+ ret = clear_user_asm(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..39847c630470 100644
--- a/arch/powerpc/lib/string_32.S
+++ b/arch/powerpc/lib/string_32.S
@@ -17,7 +17,7 @@ CACHELINE_BYTES = L1_CACHE_BYTES
LG_CACHELINE_BYTES = L1_CACHE_SHIFT
CACHELINE_MASK = (L1_CACHE_BYTES-1)
-_GLOBAL(__clear_user)
+_GLOBAL(clear_user_asm)
/*
* 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)
-EXPORT_SYMBOL(__clear_user)
+EXPORT_SYMBOL(clear_user_asm)
diff --git a/arch/powerpc/lib/string_64.S b/arch/powerpc/lib/string_64.S
index 507b18b1660e..a955f5e72feb 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.
+ * clear_user_asm: - 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
blr
-_GLOBAL_TOC(__clear_user)
+_GLOBAL_TOC(clear_user_asm)
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
-EXPORT_SYMBOL(__clear_user)
+EXPORT_SYMBOL(clear_user_asm)
--
2.20.1
