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Fix segfault on migration completion 

A simple migration reproduces it:

1. Start the source VM with:

   # qemu [...] -S

2. Start the destination VM with:

   # qemu <source VM cmd-line> -incoming tcp:0:4444

3. In the source VM:

   (qemu) migrate -d tcp:0:4444

4. The source VM will segfault as soon as migration completes (might not
   happen in the first try)

What is happening here is that qemu_file_put_notify() can end up closing
's->file' (in which case it's also set to NULL). The call stack is rather
complex, but Eduardo helped tracking it to:

select loop -> migrate_fd_put_notify() -> qemu_file_put_notify() ->
buffered_put_buffer() -> migrate_fd_put_ready() ->
migrate_fd_completed() -> migrate_fd_cleanup().

To be honest, it's not completely clear to me in which cases 's->file'
is not closed (on error maybe)? But I doubt this fix will make anything
worse.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Luiz Capitulino 2011-10-28 14:59:52 -02:00 committed by Anthony Liguori
parent 4f39d27fe4
commit 1fdc11c369
1 changed files with 1 additions and 1 deletions
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2
migration.c
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@ -216,7 +216,7 @@ static void migrate_fd_put_notify(void *opaque)
qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL); qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
qemu_file_put_notify(s->file); qemu_file_put_notify(s->file);
if (qemu_file_get_error(s->file)) { if (s->file && qemu_file_get_error(s->file)) {
migrate_fd_error(s); migrate_fd_error(s);
} }
} }