From: Kohei Enju Date: Wed, 22 Apr 2026 02:30:24 +0000 (+0000) Subject: vhost_net: fix sleeping with preempt-disabled in vhost_net_busy_poll() X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e08a9fac5cf8c3fecf4755e7e3ac059f78b8f83d;p=thirdparty%2Fkernel%2Fstable.git vhost_net: fix sleeping with preempt-disabled in vhost_net_busy_poll() syzbot reported "sleeping function called from invalid context" in vhost_net_busy_poll(). Commit 030881372460 ("vhost_net: basic polling support") introduced a busy-poll loop and preempt_{disable,enable}() around it, where each iteration calls a sleepable function inside the loop. The purpose of disabling preemption was to keep local_clock()-based timeout accounting on a single CPU, rather than as a requirement of busy-poll itself: https://lore.kernel.org/1448435489-5949-4-git-send-email-jasowang@redhat.com From this perspective, migrate_disable() is sufficient here, so replace preempt_disable() with migrate_disable(), avoiding sleepable accesses from a preempt-disabled context. Fixes: 030881372460 ("vhost_net: basic polling support") Tested-by: syzbot+6985cb8e543ea90ba8ee@syzkaller.appspotmail.com Reported-by: syzbot+6985cb8e543ea90ba8ee@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/69e6a414.050a0220.24bfd3.002d.GAE@google.com/T/ Signed-off-by: Kohei Enju Acked-by: Michael S. Tsirkin Signed-off-by: Jakub Kicinski --- diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 80965181920c..c6536cad9c4f 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -560,7 +560,7 @@ static void vhost_net_busy_poll(struct vhost_net *net, busyloop_timeout = poll_rx ? rvq->busyloop_timeout: tvq->busyloop_timeout; - preempt_disable(); + migrate_disable(); endtime = busy_clock() + busyloop_timeout; while (vhost_can_busy_poll(endtime)) { @@ -577,7 +577,7 @@ static void vhost_net_busy_poll(struct vhost_net *net, cpu_relax(); } - preempt_enable(); + migrate_enable(); if (poll_rx || sock_has_rx_data(sock)) vhost_net_busy_poll_try_queue(net, vq);