syscall: for ForkExec on Linux, always use 32-bit setgroups system call

Fixes #17092.

Change-Id: If203d802a919e00594ddc1282782fc59a083fd63
Reviewed-on: https://go-review.googlesource.com/31458Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/syscall/exec_linux.go

@@ -214,7 +214,7 @@ func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr
 		// and disabled setgroups, because otherwise unprivileged user namespace
 		// will fail with any non-empty SysProcAttr.Credential.
 		if !(sys.GidMappings != nil && !sys.GidMappingsEnableSetgroups && ngroups == 0) {
-			_, _, err1 = RawSyscall(SYS_SETGROUPS, ngroups, groups, 0)
+			_, _, err1 = RawSyscall(_SYS_setgroups, ngroups, groups, 0)
 			if err1 != 0 {
 				goto childerror
 			}

src/syscall/syscall_linux_386.go

@@ -10,8 +10,9 @@ package syscall
 import "unsafe"
 
 const (
-	_SYS_dup      = SYS_DUP2
-	_SYS_getdents = SYS_GETDENTS64
+	_SYS_dup       = SYS_DUP2
+	_SYS_getdents  = SYS_GETDENTS64
+	_SYS_setgroups = SYS_SETGROUPS32
 )
 
 func setTimespec(sec, nsec int64) Timespec {

src/syscall/syscall_linux_amd64.go

@@ -5,8 +5,9 @@
 package syscall
 
 const (
-	_SYS_dup      = SYS_DUP2
-	_SYS_getdents = SYS_GETDENTS64
+	_SYS_dup       = SYS_DUP2
+	_SYS_getdents  = SYS_GETDENTS64
+	_SYS_setgroups = SYS_SETGROUPS
 )
 
 //sys	Dup2(oldfd int, newfd int) (err error)

src/syscall/syscall_linux_arm.go

@@ -7,8 +7,9 @@ package syscall
 import "unsafe"
 
 const (
-	_SYS_dup      = SYS_DUP2
-	_SYS_getdents = SYS_GETDENTS64
+	_SYS_dup       = SYS_DUP2
+	_SYS_getdents  = SYS_GETDENTS64
+	_SYS_setgroups = SYS_SETGROUPS32
 )
 
 func setTimespec(sec, nsec int64) Timespec {

src/syscall/syscall_linux_arm64.go

@@ -5,8 +5,9 @@
 package syscall
 
 const (
-	_SYS_dup      = SYS_DUP3
-	_SYS_getdents = SYS_GETDENTS64
+	_SYS_dup       = SYS_DUP3
+	_SYS_getdents  = SYS_GETDENTS64
+	_SYS_setgroups = SYS_SETGROUPS
 )
 
 //sys	Fchown(fd int, uid int, gid int) (err error)

src/syscall/syscall_linux_mips64x.go

@@ -15,7 +15,8 @@ const (
 	// to support older kernels, we have to use getdents for mips64.
 	// Also note that struct dirent is different for these two.
 	// Lookup linux_dirent{,64} in kernel source code for details.
-	_SYS_getdents = SYS_GETDENTS
+	_SYS_getdents  = SYS_GETDENTS
+	_SYS_setgroups = SYS_SETGROUPS
 )
 
 //sys	Dup2(oldfd int, newfd int) (err error)

src/syscall/syscall_linux_ppc64x.go

@@ -8,8 +8,9 @@
 package syscall
 
 const (
-	_SYS_dup      = SYS_DUP2
-	_SYS_getdents = SYS_GETDENTS64
+	_SYS_dup       = SYS_DUP2
+	_SYS_getdents  = SYS_GETDENTS64
+	_SYS_setgroups = SYS_SETGROUPS
 )
 
 //sys	Dup2(oldfd int, newfd int) (err error)

src/syscall/syscall_linux_s390x.go

@@ -7,8 +7,9 @@ package syscall
 import "unsafe"
 
 const (
-	_SYS_dup      = SYS_DUP2
-	_SYS_getdents = SYS_GETDENTS64
+	_SYS_dup       = SYS_DUP2
+	_SYS_getdents  = SYS_GETDENTS64
+	_SYS_setgroups = SYS_SETGROUPS
 )
 
 //sys	Dup2(oldfd int, newfd int) (err error)