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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     glider@google.com, elver@google.com, <akpm@linux-foundation.org>,
        zhangpeng.00@bytedance.com
Cc:     <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
        <linuxppc-dev@lists.ozlabs.org>
Subject: [PATCH] mm: kfence: Fix false positives on big endian
Date:   Fri,  5 May 2023 13:51:27 +1000
Message-Id: <20230505035127.195387-1-mpe@ellerman.id.au>
MIME-Version: 1.0
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Precedence: bulk

Since commit 1ba3cbf3ec3b ("mm: kfence: improve the performance of
__kfence_alloc() and __kfence_free()"), kfence reports failures in
random places at boot on big endian machines.

The problem is that the new KFENCE_CANARY_PATTERN_U64 encodes the
address of each byte in its value, so it needs to be byte swapped on big
endian machines.

The compiler is smart enough to do the le64_to_cpu() at compile time, so
there is no runtime overhead.

Fixes: 1ba3cbf3ec3b ("mm: kfence: improve the performance of __kfence_alloc() and __kfence_free()")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
 mm/kfence/kfence.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h
index 2aafc46a4aaf..392fb273e7bd 100644
--- a/mm/kfence/kfence.h
+++ b/mm/kfence/kfence.h
@@ -29,7 +29,7 @@
  * canary of every 8 bytes is the same. 64-bit memory can be filled and checked
  * at a time instead of byte by byte to improve performance.
  */
-#define KFENCE_CANARY_PATTERN_U64 ((u64)0xaaaaaaaaaaaaaaaa ^ (u64)(0x0706050403020100))
+#define KFENCE_CANARY_PATTERN_U64 ((u64)0xaaaaaaaaaaaaaaaa ^ (u64)(le64_to_cpu(0x0706050403020100)))
 
 /* Maximum stack depth for reports. */
 #define KFENCE_STACK_DEPTH 64
-- 
2.40.1