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authorRussell King <rmk+kernel@armlinux.org.uk>2018-07-09 10:28:12 +0100
committerRussell King <rmk+kernel@armlinux.org.uk>2018-08-02 17:41:38 +0100
commitb1cd0a14806321721aae45f5446ed83a3647c914 (patch)
treed97f31f577fde389b410224139b342e9538c2cc5 /arch/arm
parentd09fbb327d670737ab40fd8bbb0765ae06b8b739 (diff)
downloadlinux-b1cd0a14806321721aae45f5446ed83a3647c914.tar.bz2
ARM: spectre-v1: use get_user() for __get_user()
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>
Diffstat (limited to 'arch/arm')
-rw-r--r--arch/arm/include/asm/uaccess.h17
1 files changed, 11 insertions, 6 deletions
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 29fa6f3ea25a..4140be431087 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -250,6 +250,16 @@ static inline void set_fs(mm_segment_t fs)
#define user_addr_max() \
(uaccess_kernel() ? ~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
@@ -266,12 +276,6 @@ 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); \
@@ -331,6 +335,7 @@ do { \
#define __get_user_asm_word(x, addr, err) \
__get_user_asm(x, addr, err, ldr)
+#endif
#define __put_user_switch(x, ptr, __err, __fn) \