bn/asm/x86_64-mont5.pl: fix carry bug in bn_sqr8x_internal.
CVE-2017-3732
@@ -1934,6 +1934,7 @@ __bn_sqr8x_reduction:
.align 32
.L8x_tail_done:
+ xor %rax,%rax
add (%rdx),%r8 # can this overflow?
adc \$0,%r9
adc \$0,%r10
@@ -1941,10 +1942,8 @@ __bn_sqr8x_reduction:
adc \$0,%r12
adc \$0,%r13
adc \$0,%r14
- adc \$0,%r15 # can't overflow, because we
- # started with "overhung" part
- # of multiplication
- xor %rax,%rax
+ adc \$0,%r15
+ adc \$0,%rax
neg $carry
.L8x_no_tail:
@@ -3384,6 +3383,7 @@ __bn_sqrx8x_reduction:
.align 32
.Lsqrx8x_tail_done:
+ xor %rax,%rax
add 24+8(%rsp),%r8 # can this overflow?
adc \$0,%r9
adc \$0,%r10
@@ -3391,10 +3391,8 @@ __bn_sqrx8x_reduction:
adc \$0,%r12
adc \$0,%r13
adc \$0,%r14
- adc \$0,%r15 # can't overflow, because we
- # started with "overhung" part
- # of multiplication
- mov $carry,%rax # xor %rax,%rax
+ adc \$0,%r15
+ adc \$0,%rax
sub 16+8(%rsp),$carry # mov 16(%rsp),%cf
.Lsqrx8x_no_tail: # %cf is 0 if jumped here
@@ -3409,7 +3407,7 @@ __bn_sqrx8x_reduction:
adc 8*5($tptr),%r13
adc 8*6($tptr),%r14
adc 8*7($tptr),%r15
- adc %rax,%rax # top-most carry
+ adc \$0,%rax # top-most carry
mov 32+8(%rsp),%rbx # n0
mov 8*8($tptr,%rcx),%rdx # modulo-scheduled "%r8"
