From 97ec0a816bfe1f8488355b5a6e94907a993b2cc7 Mon Sep 17 00:00:00 2001

From: Didier Spezia <[email protected]>

Date: Tue, 25 Aug 2015 16:25:11 +0000

Subject: [PATCH 07/63] [release-branch.go1.5] cmd/asm: fix potential infinite

 loop in parser

For ARM machines, the assembler supports list of registers

operands such as [R1,R2].

A list missing a ']' results in the parser issuing many errors

and consuming all the tokens. At EOF (i.e. end of the line),

it still loops.

Normally, a counter is maintained to make sure the parser

stops after 10 errors. However, multiple errors occuring on the

same line are simply ignored. Only the first one is reported.

At most one error per line is accounted.

Missing ']' in a register list therefore results in an

infinite loop.

Fixed the parser by explicitly checking for ']' to interrupt

this loops

In the operand tests, also fixed a wrong entry which I think was

not set on purpose (but still led to a successful result).

Fixes #11764

Change-Id: Ie87773388ee0d21b3a2a4cb941d4d911d0230ba4

Reviewed-on: https://go-review.googlesource.com/13920

Reviewed-by: Rob Pike <[email protected]>

Reviewed-on: https://go-review.googlesource.com/14225

---

 src/cmd/asm/internal/asm/operand_test.go | 3 ++-

 src/cmd/asm/internal/asm/parse.go        | 9 +++++++--

 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/cmd/asm/internal/asm/operand_test.go b/src/cmd/asm/internal/asm/operand_test.go

index b9154a9..01335ed 100644

--- a/src/cmd/asm/internal/asm/operand_test.go

+++ b/src/cmd/asm/internal/asm/operand_test.go

@@ -181,7 +181,7 @@ var amd64OperandTests = []operandTest{

 	{"x·y+8(SB)", "x.y+8(SB)"},

 	{"x·y+8(SP)", "x.y+8(SP)"},

 	{"y+56(FP)", "y+56(FP)"},

-	{"·AddUint32(SB", "\"\".AddUint32(SB)"},

+	{"·AddUint32(SB)", "\"\".AddUint32(SB)"},

 	{"·callReflect(SB)", "\"\".callReflect(SB)"},

 }

@@ -288,6 +288,7 @@ var armOperandTests = []operandTest{

 	{"runtime·_sfloat2(SB)", "runtime._sfloat2(SB)"},

 	{"·AddUint32(SB)", "\"\".AddUint32(SB)"},

 	{"(R1, R3)", "(R1, R3)"},

+	{"[R0,R1,g,R15", ""}, // Issue 11764 - previously asm just hung parsing ']' missing register lists

 }

 var ppc64OperandTests = []operandTest{

diff --git a/src/cmd/asm/internal/asm/parse.go b/src/cmd/asm/internal/asm/parse.go

index c07e6f8..6cf50df 100644

--- a/src/cmd/asm/internal/asm/parse.go

+++ b/src/cmd/asm/internal/asm/parse.go

@@ -698,10 +698,15 @@ func (p *Parser) registerIndirect(a *obj.Addr, prefix rune) {

 func (p *Parser) registerList(a *obj.Addr) {

 	// One range per loop.

 	var bits uint16

+ListLoop:

 	for {

 		tok := p.next()

-		if tok.ScanToken == ']' {

-			break

+		switch tok.ScanToken {

+		case ']':

+			break ListLoop

+		case scanner.EOF:

+			p.errorf("missing ']' in register list")

+			return

 		}

 		lo := p.registerNumber(tok.String())

 		hi := lo

-- 

2.6.1