CVE-2021-44717

Origin: https://github.com/golang/net/commit/44a3fb49d99cc8a4de4925b69650f97bb07faf1d
Reviewed-by: Sylvain Beucler <beuc@debian.org>
Last-Update: 2022-04-18

From 44a3fb49d99cc8a4de4925b69650f97bb07faf1d Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Wed, 8 Dec 2021 18:05:11 -0500
Subject: [PATCH] [release-branch.go1.16] syscall: fix ForkLock spurious
 close(0) on pipe failure

Pipe (and therefore forkLockPipe) does not make any guarantees
about the state of p after a failed Pipe(p). Avoid that assumption
and the too-clever goto, so that we don't accidentally Close a real fd
if the failed pipe leaves p[0] or p[1] set >= 0.

Updates #50057
Fixes CVE-2021-44717

Change-Id: Iff8e19a6efbba0c73cc8b13ecfae381c87600bb4
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1291270
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/370514
Trust: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Alex Rakoczy <alex@golang.org>
Gbp-Pq: Name CVE-2021-44717.patch

diff --git a/src/syscall/exec_unix.go b/src/syscall/exec_unix.go
index 9a950ac17fdbe5d4defd619a366916c5816bb38c..2186f93d6a4c20baef04c066ff641d7bb070187d 100644 (file)
--- a/src/syscall/exec_unix.go
+++ b/src/syscall/exec_unix.go
@@ -144,9 +144,6 @@ func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error)
                sys = &zeroSysProcAttr
        }
 
-       p[0] = -1
-       p[1] = -1
-
        // Convert args to C form.
        argv0p, err := BytePtrFromString(argv0)
        if err != nil {
@@ -187,14 +184,17 @@ func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error)
 
        // Allocate child status pipe close on exec.
        if err = forkExecPipe(p[:]); err != nil {
-               goto error
+               ForkLock.Unlock()
+               return 0, err
        }
 
        // Kick off child.
        pid, err1 = forkAndExecInChild(argv0p, argvp, envvp, chroot, dir, attr, sys, p[1])
        if err1 != 0 {
-               err = Errno(err1)
-               goto error
+               Close(p[0])
+               Close(p[1])
+               ForkLock.Unlock()
+               return 0, Errno(err1)
        }
        ForkLock.Unlock()
 
@@ -221,14 +221,6 @@ func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error)
 
        // Read got EOF, so pipe closed on exec, so exec succeeded.
        return pid, nil
-
-error:
-       if p[0] >= 0 {
-               Close(p[0])
-               Close(p[1])
-       }
-       ForkLock.Unlock()
-       return 0, err
 }
 
 // Combination of fork and exec, careful to be thread safe.