Commit 386a5a1e authored by Amit Shah's avatar Amit Shah
Browse files

char: remove watch callback on chardev detach from frontend 

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 segfault.

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-stable@nongnu.org>
Reported-by: default avatarSibiao Luo <sluo@redhat.com>
Reviewed-by: default avatarGerd Hoffmann <kraxel@redhat.com>
Signed-off-by: default avatarAmit Shah <amit.shah@redhat.com>
parent 26da70c7

qemu-char.c

+3 −0
Original line number Diff line number Diff line
@@ -193,6 +193,8 @@ void qemu_chr_fe_printf(CharDriverState *s, const char *fmt, ...) 
    va_end(ap);

}



static void remove_fd_in_watch(CharDriverState *chr);



void qemu_chr_add_handlers(CharDriverState *s,

                           IOCanReadHandler *fd_can_read,

                           IOReadHandler *fd_read,
@@ -203,6 +205,7 @@ void qemu_chr_add_handlers(CharDriverState *s, 


    if (!opaque && !fd_can_read && !fd_read && !fd_event) {

        fe_open = 0;

        remove_fd_in_watch(s);

    } else {

        fe_open = 1;

    }