From: Ard Biesheuvel <ardb@kernel•org>
To: linux@armlinux•org.uk
Cc: linux-arm-kernel@lists•infradead.org, arnd@arndb•de,
linus.walleij@linaro•org, Ard Biesheuvel <ardb@kernel•org>,
stable@vger•kernel.org
Subject: [PATCH] ARM: uaccess: avoid alignment faults in copy_[from|to]_kernel_nofault
Date: Tue, 18 Jan 2022 09:28:08 +0100 [thread overview]
Message-ID: <20220118082808.931129-1-ardb@kernel.org> (raw)
The helpers that are used to implement copy_from_kernel_nofault() and
copy_to_kernel_nofault() cast a void* to a pointer to a wider type,
which may result in alignment faults on ARM if the compiler decides to
use double-word or multiple-word load/store instructions.
So use the unaligned accessors where needed: when the type's size > 1
and the input was not aligned already by the caller.
Cc: <stable@vger•kernel.org>
Fixes: 2df4c9a741a0 ("ARM: 9112/1: uaccess: add __{get,put}_kernel_nofault")
Signed-off-by: Ard Biesheuvel <ardb@kernel•org>
---
arch/arm/include/asm/uaccess.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 36fbc3329252..32dbfd81f42a 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -11,6 +11,7 @@
#include <linux/string.h>
#include <asm/memory.h>
#include <asm/domain.h>
+#include <asm/unaligned.h>
#include <asm/unified.h>
#include <asm/compiler.h>
@@ -497,7 +498,10 @@ do { \
} \
default: __err = __get_user_bad(); break; \
} \
- *(type *)(dst) = __val; \
+ if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) \
+ put_unaligned(__val, (type *)(dst)); \
+ else \
+ *(type *)(dst) = __val; /* aligned by caller */ \
if (__err) \
goto err_label; \
} while (0)
@@ -507,7 +511,9 @@ do { \
const type *__pk_ptr = (dst); \
unsigned long __dst = (unsigned long)__pk_ptr; \
int __err = 0; \
- type __val = *(type *)src; \
+ type __val = IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) \
+ ? get_unaligned((type *)(src)) \
+ : *(type *)(src); /* aligned by caller */ \
switch (sizeof(type)) { \
case 1: __put_user_asm_byte(__val, __dst, __err, ""); break; \
case 2: __put_user_asm_half(__val, __dst, __err, ""); break; \
--
2.30.2
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next reply other threads:[~2022-01-18 8:29 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-18 8:28 Ard Biesheuvel [this message]
2022-01-18 8:38 ` [PATCH] ARM: uaccess: avoid alignment faults in copy_[from|to]_kernel_nofault Arnd Bergmann
2022-01-18 8:41 ` Ard Biesheuvel
2022-01-18 13:00 ` Ard Biesheuvel
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