arm64: Avoid premature usercopy failure for __arch_copy_to_user_generic_read

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5MJU8


CVE: NA

---------------------------------

Commit 1b1b4ded ("arm64: Avoid premature usercopy failure") fixes an
usercopy failure issues, it introduced a variable srcin and used it in
fixup routine, but the variable is not initialized in
__arch_copy_to_user_generic_read(), this will cause an illegal pointer
issue in fixup.

Fixes: 1b1b4ded ("arm64: Avoid premature usercopy failure")
Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
Tested-by: yongqiang Liu <liuyongqiang13@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>

arch/arm64/lib/copy_to_user.S

@@ -77,6 +77,7 @@ ENDPROC(__arch_copy_to_user)
 ENTRY(__arch_copy_to_user_generic_read)
 	uaccess_enable_not_uao x3, x4, x5
 	add	end, x0, x2
+	mov	srcin, x1
 #include "copy_template_generic_read.S"
 	uaccess_disable_not_uao x3, x4