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authorRussell King <rmk+kernel@armlinux.org.uk>2018-10-04 00:56:05 -0400
committerDavid A. Long <dave.long@linaro.org>2018-10-30 23:23:46 -0400
commit518029530e79cc29a8b32d24903a0be22257e9fc (patch)
tree46beaaed9259259d162d750246beccb6bda5989b
parent142fee8a5498ccd0a377d20c5072b7dc9a2c359b (diff)
downloadlinux-linaro-stable-518029530e79cc29a8b32d24903a0be22257e9fc.tar.gz
ARM: spectre-v1: use get_user() for __get_user()
Commit b1cd0a14806321721aae45f5446ed83a3647c914 upstream. Fixing __get_user() for spectre variant 1 is not sane: we would have to add address space bounds checking in order to validate that the location should be accessed, and then zero the address if found to be invalid. Since __get_user() is supposed to avoid the bounds check, and this is exactly what get_user() does, there's no point having two different implementations that are doing the same thing. So, when the Spectre workarounds are required, make __get_user() an alias of get_user(). Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> Signed-off-by: David A. Long <dave.long@linaro.org>
-rw-r--r--arch/arm/include/asm/uaccess.h16
1 files changed, 10 insertions, 6 deletions
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 968b50063431..ecd159b45f12 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -314,6 +314,15 @@ static inline void set_fs(mm_segment_t fs)
#define user_addr_max() \
(segment_eq(get_fs(), KERNEL_DS) ? ~0UL : get_fs())
+#ifdef CONFIG_CPU_SPECTRE
+/*
+ * When mitigating Spectre variant 1, it is not worth fixing the non-
+ * verifying accessors, because we need to add verification of the
+ * address space there. Force these to use the standard get_user()
+ * version instead.
+ */
+#define __get_user(x, ptr) get_user(x, ptr)
+#else
/*
* The "__xxx" versions of the user access functions do not verify the
* address space - it must have been done previously with a separate
@@ -330,12 +339,6 @@ static inline void set_fs(mm_segment_t fs)
__gu_err; \
})
-#define __get_user_error(x, ptr, err) \
-({ \
- __get_user_err((x), (ptr), err); \
- (void) 0; \
-})
-
#define __get_user_err(x, ptr, err) \
do { \
unsigned long __gu_addr = (unsigned long)(ptr); \
@@ -395,6 +398,7 @@ do { \
#define __get_user_asm_word(x, addr, err) \
__get_user_asm(x, addr, err, ldr)
+#endif
#define __put_user(x, ptr) \
({ \