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char: remove watch callback on chardev detach from frontend

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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: Sibiao Luo <sluo@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
This commit is contained in:
Amit Shah 2013-08-28 15:24:05 +05:30
parent 26da70c725
commit 386a5a1e00
1 changed files with 3 additions and 0 deletions
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3
qemu-char.c
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@ -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;
}