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Commit f4438f29 authored by Russell King's avatar Russell King Committed by Greg Kroah-Hartman
Browse files

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: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: default avatarDavid A. Long <dave.long@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent bdf0f17e

arch/arm/include/asm/uaccess.h

+11 −6
Original line number Diff line number Diff line
@@ -280,6 +280,16 @@ 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
@@ -296,12 +306,6 @@ 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);			\
@@ -361,6 +365,7 @@ 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)				\