os/user: fix buffer retry loop on macOS

getpwnam_r and friends return the errno as the result,
not in the global errno. The code changes in CL 449316
inadvertently started using the global errno.
So if a lookup didn't fit in the first buffer size,
it was treated as not found instead of growing the buffer.

Fixes #56942.

Change-Id: Ic5904fbeb31161bccd858e5adb987e919fb3e9d9
Reviewed-on: https://go-review.googlesource.com/c/go/+/455815
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Russ Cox <rsc@golang.org>

diff --git a/src/internal/syscall/unix/user_darwin.go b/src/internal/syscall/unix/user_darwin.go
index cfbc02917d05867ace73c2e8134897dea323433a..d05acdaa490514f22b12870f0a24cf18b80e0b50 100644 (file)
--- a/src/internal/syscall/unix/user_darwin.go
+++ b/src/internal/syscall/unix/user_darwin.go
@@ -52,56 +52,60 @@ type Group struct {
 func libc_getpwnam_r_trampoline()
 
 func Getpwnam(name *byte, pwd *Passwd, buf *byte, size uintptr, result **Passwd) syscall.Errno {
-       _, _, errno := syscall_syscall6(abi.FuncPCABI0(libc_getpwnam_r_trampoline),
+       // Note: Returns an errno as its actual result, not in global errno.
+       errno, _, _ := syscall_syscall6(abi.FuncPCABI0(libc_getpwnam_r_trampoline),
                uintptr(unsafe.Pointer(name)),
                uintptr(unsafe.Pointer(pwd)),
                uintptr(unsafe.Pointer(buf)),
                size,
                uintptr(unsafe.Pointer(result)),
                0)
-       return errno
+       return syscall.Errno(errno)
 }
 
 //go:cgo_import_dynamic libc_getpwuid_r getpwuid_r  "/usr/lib/libSystem.B.dylib"
 func libc_getpwuid_r_trampoline()
 
 func Getpwuid(uid uint32, pwd *Passwd, buf *byte, size uintptr, result **Passwd) syscall.Errno {
-       _, _, errno := syscall_syscall6(abi.FuncPCABI0(libc_getpwuid_r_trampoline),
+       // Note: Returns an errno as its actual result, not in global errno.
+       errno, _, _ := syscall_syscall6(abi.FuncPCABI0(libc_getpwuid_r_trampoline),
                uintptr(uid),
                uintptr(unsafe.Pointer(pwd)),
                uintptr(unsafe.Pointer(buf)),
                size,
                uintptr(unsafe.Pointer(result)),
                0)
-       return errno
+       return syscall.Errno(errno)
 }
 
 //go:cgo_import_dynamic libc_getgrnam_r getgrnam_r  "/usr/lib/libSystem.B.dylib"
 func libc_getgrnam_r_trampoline()
 
 func Getgrnam(name *byte, grp *Group, buf *byte, size uintptr, result **Group) syscall.Errno {
-       _, _, errno := syscall_syscall6(abi.FuncPCABI0(libc_getgrnam_r_trampoline),
+       // Note: Returns an errno as its actual result, not in global errno.
+       errno, _, _ := syscall_syscall6(abi.FuncPCABI0(libc_getgrnam_r_trampoline),
                uintptr(unsafe.Pointer(name)),
                uintptr(unsafe.Pointer(grp)),
                uintptr(unsafe.Pointer(buf)),
                size,
                uintptr(unsafe.Pointer(result)),
                0)
-       return errno
+       return syscall.Errno(errno)
 }
 
 //go:cgo_import_dynamic libc_getgrgid_r getgrgid_r  "/usr/lib/libSystem.B.dylib"
 func libc_getgrgid_r_trampoline()
 
 func Getgrgid(gid uint32, grp *Group, buf *byte, size uintptr, result **Group) syscall.Errno {
-       _, _, errno := syscall_syscall6(abi.FuncPCABI0(libc_getgrgid_r_trampoline),
+       // Note: Returns an errno as its actual result, not in global errno.
+       errno, _, _ := syscall_syscall6(abi.FuncPCABI0(libc_getgrgid_r_trampoline),
                uintptr(gid),
                uintptr(unsafe.Pointer(grp)),
                uintptr(unsafe.Pointer(buf)),
                size,
                uintptr(unsafe.Pointer(result)),
                0)
-       return errno
+       return syscall.Errno(errno)
 }
 
 //go:cgo_import_dynamic libc_sysconf sysconf "/usr/lib/libSystem.B.dylib"

diff --git a/src/os/user/cgo_lookup_unix.go b/src/os/user/cgo_lookup_unix.go
index 81787fee2bebbb2f54e7af5fdf0807afc1ea164d..b745ffd9cf44ea8675de0abe5d0912af822de280 100644 (file)
--- a/src/os/user/cgo_lookup_unix.go
+++ b/src/os/user/cgo_lookup_unix.go
@@ -141,7 +141,7 @@ func buildGroup(grp *_C_struct_group) *Group {
 
 type bufferKind _C_int
 
-const (
+var (
        userBuffer  = bufferKind(_C__SC_GETPW_R_SIZE_MAX)
        groupBuffer = bufferKind(_C__SC_GETGR_R_SIZE_MAX)
 )

diff --git a/src/os/user/lookup_plan9.go b/src/os/user/lookup_plan9.go
index dcc9319268807f9c61ee8b46b2f95ce191ece904..c2aabd504c5baad2ce4359f71366bd35954e2885 100644 (file)
--- a/src/os/user/lookup_plan9.go
+++ b/src/os/user/lookup_plan9.go
@@ -20,6 +20,13 @@ func init() {
        groupListImplemented = false
 }
 
+var (
+       // unused variables (in this implementation)
+       // modified during test to exercise code paths in the cgo implementation.
+       userBuffer  = 0
+       groupBuffer = 0
+)
+
 func current() (*User, error) {
        ubytes, err := os.ReadFile("/dev/user")
        if err != nil {

diff --git a/src/os/user/lookup_stubs.go b/src/os/user/lookup_stubs.go
index b02c1ffa284f93f47ed02b34a74e561dace66bff..89dfe455b546e8d1df48e526637d022ebfcee1b5 100644 (file)
--- a/src/os/user/lookup_stubs.go
+++ b/src/os/user/lookup_stubs.go
@@ -13,6 +13,13 @@ import (
        "strconv"
 )
 
+var (
+       // unused variables (in this implementation)
+       // modified during test to exercise code paths in the cgo implementation.
+       userBuffer  = 0
+       groupBuffer = 0
+)
+
 func current() (*User, error) {
        uid := currentUID()
        // $USER and /etc/passwd may disagree; prefer the latter if we can get it.

diff --git a/src/os/user/lookup_windows.go b/src/os/user/lookup_windows.go
index f65773ced3a36d04ddaca2a1eaa2aeedad580673..e64b8ae0286f99e50cbf91bc0c46c710415764f6 100644 (file)
--- a/src/os/user/lookup_windows.go
+++ b/src/os/user/lookup_windows.go
@@ -192,6 +192,13 @@ func newUser(uid, gid, dir, username, domain string) (*User, error) {
        return u, nil
 }
 
+var (
+       // unused variables (in this implementation)
+       // modified during test to exercise code paths in the cgo implementation.
+       userBuffer  = 0
+       groupBuffer = 0
+)
+
 func current() (*User, error) {
        t, e := syscall.OpenCurrentProcessToken()
        if e != nil {

diff --git a/src/os/user/user_test.go b/src/os/user/user_test.go
index 80251749a7d670e4306aa60abce77583b728cdba..0fa963dae07d9db1a9f799111fcef8cd97c907c4 100644 (file)
--- a/src/os/user/user_test.go
+++ b/src/os/user/user_test.go
@@ -16,6 +16,11 @@ func checkUser(t *testing.T) {
 }
 
 func TestCurrent(t *testing.T) {
+       old := userBuffer
+       defer func() {
+               userBuffer = old
+       }()
+       userBuffer = 1 // force use of retry code
        u, err := Current()
        if err != nil {
                t.Fatalf("Current: %v (got %#v)", err, u)
@@ -91,6 +96,11 @@ func checkGroup(t *testing.T) {
 }
 
 func TestLookupGroup(t *testing.T) {
+       old := groupBuffer
+       defer func() {
+               groupBuffer = old
+       }()
+       groupBuffer = 1 // force use of retry code
        checkGroup(t)
        user, err := Current()
        if err != nil {