[release-branch.go1.17] 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/+/370534
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>
diff --git a/src/syscall/exec_unix.go b/src/syscall/exec_unix.go
index 54b18dc..c9c9d1a 100644
--- a/src/syscall/exec_unix.go
+++ b/src/syscall/exec_unix.go
@@ -153,9 +153,6 @@
sys = &zeroSysProcAttr
}
- p[0] = -1
- p[1] = -1
-
// Convert args to C form.
argv0p, err := BytePtrFromString(argv0)
if err != nil {
@@ -205,14 +202,17 @@
// 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()
@@ -244,14 +244,6 @@
// 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.
