$ go version
go version devel +0449858880be Mon Aug 11 17:11:31 2014 -0400 linux/amd64
$ go get -u -a code.google.com/p/go.tools/cmd/vet
$ go vet syscall
$ go vet -x syscall
../pkg/tool/linux_amd64/vet pkg/syscall/creds_test.go pkg/syscall/env_unix.go
pkg/syscall/exec_linux.go pkg/syscall/exec_unix.go pkg/syscall/flock.go
pkg/syscall/lsf_linux.go pkg/syscall/mmap_unix_test.go pkg/syscall/netlink_linux.go
pkg/syscall/race0.go pkg/syscall/sockcmsg_linux.go pkg/syscall/sockcmsg_unix.go
pkg/syscall/str.go pkg/syscall/syscall.go pkg/syscall/syscall_linux.go
pkg/syscall/syscall_linux_amd64.go pkg/syscall/syscall_test.go
pkg/syscall/syscall_unix.go pkg/syscall/syscall_unix_test.go
pkg/syscall/zerrors_linux_amd64.go pkg/syscall/zsyscall_linux_amd64.go
pkg/syscall/zsysnum_linux_amd64.go pkg/syscall/ztypes_linux_amd64.go
pkg/syscall/asm_linux_amd64.s
$ ../pkg/tool/linux_amd64/vet pkg/syscall/creds_test.go pkg/syscall/env_unix.go
pkg/syscall/exec_linux.go pkg/syscall/exec_unix.go pkg/syscall/flock.go
pkg/syscall/lsf_linux.go pkg/syscall/mmap_unix_test.go pkg/syscall/netlink_linux.go
pkg/syscall/race0.go pkg/syscall/sockcmsg_linux.go pkg/syscall/sockcmsg_unix.go
pkg/syscall/str.go pkg/syscall/syscall.go pkg/syscall/syscall_linux.go
pkg/syscall/syscall_linux_amd64.go pkg/syscall/syscall_test.go
pkg/syscall/syscall_unix.go pkg/syscall/syscall_unix_test.go
pkg/syscall/zerrors_linux_amd64.go pkg/syscall/zsyscall_linux_amd64.go
pkg/syscall/zsysnum_linux_amd64.go pkg/syscall/ztypes_linux_amd64.go
pkg/syscall/asm_linux_amd64.s
$ ../pkg/tool/linux_amd64/vet syscall
vet: error walking tree: stat syscall: no such file or directory
vet: syscall: open syscall: no such file or directory
vet: no files checked
$ ../pkg/tool/linux_amd64/vet pkg/syscall
pkg/syscall/sockcmsg_unix.go:82: possible misuse of unsafe.Pointer
$ (cd ~/src/code.google.com/p/go.tools/; hg sum)
parent: 1035:35238aaf7394 tip
 go.tools/go/ssa: improvements to CreateTestMainPackage.
branch: default
commit: 1 unknown (clean)
update: (current)


I also tried go1.3 with vet from release-branch.go1.3 package.
It's the same.

And with our official 1.3 binary.
$ wget http://golang.org/dl/go1.3.linux-amd64.tar.gz
$ tar xf go1.3.linux-amd64.tar.gz
$ cd go
$ GOROOT=`pwd` bin/go vet syscall
$ GOROOT=`pwd` bin/go tool vet src/pkg/syscall
src/pkg/syscall/sockcmsg_unix.go:82: possible misuse of unsafe.Pointer

It's because there is a difference between vet on Darwin and Linux?

Originated from the discussion "[golang-dev] proposal: unsafe.Pointer arithmetic
rules".
Tentatively marked Go 1.3.1 as go1.3 also suffered from this (at least on linux), and
the affected vet check is important enough to release the fix in 1.3.1.