leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

ARM: 9179/1: uaccess: avoid alignment faults in copy_[from|to]_kernel_nofault

Browse Source 
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.

Only configurations that define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y
are affected, given that commit 2423de2e6f ("ARM: 9115/1: mm/maccess:
fix unaligned copy_{from,to}_kernel_nofault") ensures that dst and src
are sufficiently aligned otherwise.

So use the unaligned accessors for accessing dst and src in cases where
they may be misaligned.

Cc: <stable@vger.kernel.org> # depends on 2423de2e6f
Fixes: 2df4c9a741 ("ARM: 9112/1: uaccess: add __{get,put}_kernel_nofault")
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Ard Biesheuvel 2022-01-18 13:45:09 +01:00 committed by Russell King (Oracle)
parent 8b59b0a53c
commit 15420269b0
1 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
arch/arm/include/asm/uaccess.h
View File

@ -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; \