Patchwork [3/3] char: remove watch callback on chardev detach from frontend

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Submitter Amit Shah
Date Sept. 5, 2013, 6:27 p.m.
Message ID <386a5a1e0057e220f79c48fe3689e3dfb17f1b09.1378386450.git.amit.shah@redhat.com>
Download mbox | patch
Permalink /patch/272931/
State New
Headers show

Comments

Amit Shah - Sept. 5, 2013, 6:27 p.m.
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>
---
 qemu-char.c | 3 +++
 1 file changed, 3 insertions(+)

Patch

diff --git a/qemu-char.c b/qemu-char.c
index 0a0833f..6f111ab 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -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;
     }