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vsock: initialize child_ns_mode_locked in vsock_net_init()

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JIRA: https://issues.redhat.com/browse/RHEL-155389

commit b18c833888742ca9de80c250f9d40d0e97caa9f6
Author: Stefano Garzarella <sgarzare@redhat.com>
Date:   Wed Apr 1 11:21:53 2026 +0200

    vsock: initialize child_ns_mode_locked in vsock_net_init()

    The `child_ns_mode_locked` field lives in `struct net`, which persists
    across vsock module reloads. When the module is unloaded and reloaded,
    `vsock_net_init()` resets `mode` and `child_ns_mode` back to their
    default values, but does not reset `child_ns_mode_locked`.

    The stale lock from the previous module load causes subsequent writes
    to `child_ns_mode` to silently fail: `vsock_net_set_child_mode()` sees
    the old lock, skips updating the actual value, and returns success
    when the requested mode matches the stale lock. The sysctl handler
    reports no error, but `child_ns_mode` remains unchanged.

    Steps to reproduce:
        $ modprobe vsock
        $ echo local > /proc/sys/net/vsock/child_ns_mode
        $ cat /proc/sys/net/vsock/child_ns_mode
        local
        $ modprobe -r vsock
        $ modprobe vsock
        $ echo local > /proc/sys/net/vsock/child_ns_mode
        $ cat /proc/sys/net/vsock/child_ns_mode
        global    <--- expected "local"

    Fix this by initializing `child_ns_mode_locked` to 0 (unlocked) in
    `vsock_net_init()`, so the write-once mechanism works correctly after
    module reload.

    Fixes: 102eab95f025 ("vsock: lock down child_ns_mode as write-once")
    Reported-by: Jin Liu <jinl@redhat.com>
    Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
    Reviewed-by: Bobby Eshleman <bobbyeshleman@meta.com>
    Link: https://patch.msgid.link/20260401092153.28462-1-sgarzare@redhat.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
This commit is contained in:
Stefano Garzarella
2026-07-17 11:19:30 +02:00
parent 49953a2444
commit 99f2f5b74c
1 changed files with 1 additions and 0 deletions
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net/vmw_vsock/af_vsock.c
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@@ -2791,6 +2791,7 @@ static void vsock_net_init(struct net *net)
net->vsock.mode = vsock_net_child_mode(current->nsproxy->net_ns);
net->vsock.child_ns_mode = net->vsock.mode;
net->vsock.child_ns_mode_locked = 0;
}
static __net_init int vsock_sysctl_init_net(struct net *net)