[PATCH] powerpc/code-patching: Disable KASAN in __patch_instructions()

[Benjamin Gray <bgray@linux.ibm.com>]

The memset/memcpy functions are by default instrumented by KASAN, which
complains about user memory access when using a poking page in
userspace.

Using a userspace address is expected though, so don't instrument with
KASAN for this function.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>

---

I tried to replace the memsetN calls with __memsetN, but we appear to
disable the non-instrumented variants of these when KASAN is enabled.
Christophe might you know more here?

The cost of just suppressing reports for this section shouldn't be too
relevant; KASAN detects the access, but exits before it starts preparing
the report itself. So it's just like any other KASAN instrumented
function for the most part.
---
 arch/powerpc/lib/code-patching.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index c6ab46156cda..24989594578a 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -3,6 +3,7 @@
  *  Copyright 2008 Michael Ellerman, IBM Corporation.
  */
 
+#include <linux/kasan.h>
 #include <linux/kprobes.h>
 #include <linux/mmu_context.h>
 #include <linux/random.h>
@@ -377,6 +378,7 @@ static int __patch_instructions(u32 *patch_addr, u32 *code, size_t len, bool rep
 	unsigned long start = (unsigned long)patch_addr;
 
 	/* Repeat instruction */
+	kasan_disable_current();
 	if (repeat_instr) {
 		ppc_inst_t instr = ppc_inst_read(code);
 
@@ -392,6 +394,7 @@ static int __patch_instructions(u32 *patch_addr, u32 *code, size_t len, bool rep
 	} else {
 		memcpy(patch_addr, code, len);
 	}
+	kasan_enable_current();
 
 	smp_wmb();	/* smp write barrier */
 	flush_icache_range(start, start + len);
-- 
2.43.0