From bf10e2c3682e75c53f6109d758737dcb9fc01482 Mon Sep 17 00:00:00 2001
From: zbarsky-openai <zbarsky@openai.com>
Date: Mon, 24 Aug 2026 11:48:16 -0400
Subject: [PATCH] vm: enable isolated System V IPC for sandboxed actions

PostgreSQL initialization inside an actiond action currently fails with:

```text
FATAL:  could not create shared memory segment: Function not implemented
DETAIL:  Failed system call was shmget(key=4140, size=56, 03600).
```

Enable System V IPC and IPC namespaces in both supported guest-kernel
configurations, and give every action its own IPC namespace. Isolating IPC at
the action boundary prevents shared-memory segments, semaphore sets, and
message queues from leaking between unrelated executions.

Extend the existing clone-flags test to cover IPC namespace isolation. Both
architecture configurations resolve through the real Linux Kconfig parser. The
ARM64 guest kernel and initramfs build through actiond, and the original
PostgreSQL/pgvector integration test passes against the rebuilt guest.
---
 src/action_runner.zig  | 5 +++--
 vm/linux.config        | 2 ++
 vm/linux_x86_64.config | 2 ++
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/action_runner.zig b/src/action_runner.zig
index 0ecbb14..8bc0ebd 100644
--- a/src/action_runner.zig
+++ b/src/action_runner.zig
@@ -45,7 +45,7 @@ inline fn runnerTimingNow(io: std.Io) std.Io.Timestamp {
 
 fn actionNamespaceFlags() usize {
     const linux = std.os.linux;
-    return linux.CLONE.NEWNS | linux.CLONE.NEWNET | linux.CLONE.NEWPID;
+    return linux.CLONE.NEWNS | linux.CLONE.NEWNET | linux.CLONE.NEWPID | linux.CLONE.NEWIPC;
 }
 
 fn actionCloneFlags() u32 {
@@ -1637,12 +1637,13 @@ test "ExecutionControl rejects a cancelled action" {
     try std.testing.expectError(error.ExecutionCancelled, execution_control.check(std.testing.io));
 }
 
-test "action clone flags isolate mounts, networking, and action process IDs" {
+test "action clone flags isolate mounts, networking, process IDs, and IPC" {
     const linux = std.os.linux;
     const flags = actionCloneFlags();
     try std.testing.expect((flags & linux.CLONE.NEWNS) != 0);
     try std.testing.expect((flags & linux.CLONE.NEWNET) != 0);
     try std.testing.expect((flags & linux.CLONE.NEWPID) != 0);
+    try std.testing.expect((flags & linux.CLONE.NEWIPC) != 0);
     try std.testing.expectEqual(@as(u32, @intFromEnum(linux.SIG.CHLD)), flags & linux.CSIGNAL);
 }
 
diff --git a/vm/linux.config b/vm/linux.config
index 69abcd9..34de9d5 100644
--- a/vm/linux.config
+++ b/vm/linux.config
@@ -36,6 +36,7 @@ CONFIG_HYPERV_STORAGE=y
 CONFIG_HYPERV_VMBUS=y
 CONFIG_HYPERV_VSOCKETS=y
 CONFIG_INET=y
+CONFIG_IPC_NS=y
 CONFIG_JBD2=y
 CONFIG_KALLSYMS=y
 CONFIG_MEMCG=y
@@ -61,6 +62,7 @@ CONFIG_SCSI_COMMON=y
 CONFIG_SCSI_LOWLEVEL=y
 CONFIG_SIGNALFD=y
 CONFIG_SYSFS=y
+CONFIG_SYSVIPC=y
 CONFIG_SQUASHFS=y
 CONFIG_SQUASHFS_ZSTD=y
 CONFIG_TMPFS=y
diff --git a/vm/linux_x86_64.config b/vm/linux_x86_64.config
index 278a71f..f6b17d4 100644
--- a/vm/linux_x86_64.config
+++ b/vm/linux_x86_64.config
@@ -33,6 +33,7 @@ CONFIG_FS_MBCACHE=y
 # CONFIG_FUSE_FS is not set
 CONFIG_FUTEX=y
 CONFIG_INET=y
+CONFIG_IPC_NS=y
 CONFIG_JBD2=y
 CONFIG_KALLSYMS=y
 CONFIG_KERNEL_LZ4=y
@@ -54,6 +55,7 @@ CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SIGNALFD=y
 CONFIG_SYSFS=y
+CONFIG_SYSVIPC=y
 CONFIG_SQUASHFS=y
 CONFIG_SQUASHFS_ZSTD=y
 CONFIG_TMPFS=y