If a frontend device releases the chardev (via unplug), the chr handlers are set to NULL via qdev's exit callbacks invoking qemu_chr_add_handlers(). If the chardev had a pending operation, a callback will be invoked, which will try to access data in the just-released frontend, causing a NULL pointer dereference.
Ensure the callbacks are disabled when frontends release chardevs. This was seen when a virtio-serial port was unplugged when heavy guest->host IO was in progress (causing a callback to be registered). In the window in which the throttling was active, unplugging ports caused a qemu segfault. https://bugzilla.redhat.com/show_bug.cgi?id=985205 CC: <qemu-sta...@nongnu.org> Reported-by: Sibiao Luo <s...@redhat.com> Signed-off-by: Amit Shah <amit.s...@redhat.com> --- include/sysemu/char.h | 1 + qemu-char.c | 3 +++ 2 files changed, 4 insertions(+) diff --git a/include/sysemu/char.h b/include/sysemu/char.h index 8053130..3400b04 100644 --- a/include/sysemu/char.h +++ b/include/sysemu/char.h @@ -69,6 +69,7 @@ struct CharDriverState { void (*chr_accept_input)(struct CharDriverState *chr); void (*chr_set_echo)(struct CharDriverState *chr, bool echo); void (*chr_set_fe_open)(struct CharDriverState *chr, int fe_open); + void (*chr_detach)(struct CharDriverState *chr); void *opaque; char *label; char *filename; diff --git a/qemu-char.c b/qemu-char.c index 6259496..f27fdb6 100644 --- a/qemu-char.c +++ b/qemu-char.c @@ -203,6 +203,9 @@ void qemu_chr_add_handlers(CharDriverState *s, if (!opaque && !fd_can_read && !fd_read && !fd_event) { fe_open = 0; + if (s->handler_opaque && s->chr_detach) { + s->chr_detach(s); + } } else { fe_open = 1; } -- 1.8.3.1
