From: Russell King rmk+kernel@armlinux.org.uk
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm/include/asm/uaccess.h | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-)
--- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -288,6 +288,16 @@ static inline void set_fs(mm_segment_t f #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 @@ -304,12 +314,6 @@ static inline void set_fs(mm_segment_t f __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); \ @@ -369,6 +373,7 @@ 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) \