virtio_console: fix hot-unplug races in TX paths

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When a port is hot-unplugged, unplug_port() nullifies port->portdev.
However, concurrent TX paths (__send_to_port, put_chars) could read a
stale pointer or encounter a NULL pointer dereference.

Add READ_ONCE(port->portdev) and NULL checks in the TX paths. In
__send_to_port(), move the out_vq assignment inside the outvq_lock and
check portdev under the lock. Correspondingly, update unplug_port() to
NULL out port->portdev while holding the outvq_lock to serialize with
__send_to_port().

In put_chars(), return count instead of 0 on unplug to prevent the hvc
layer from spinning in an infinite retry loop.

Signed-off-by: Sungho Bae <baver.bae@lge.com>
Link: https://patch.msgid.link/20260603183757.21587-3-baver.bae@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Sungho Bae 2026-06-04 03:37:55 +09:00 • committed by Greg Kroah-Hartman

parent fc220d6be3

commit a616ad344d

1 changed files with 31 additions and 6 deletions

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drivers/char/virtio_console.c

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