75 lines
3.0 KiB
Diff
75 lines
3.0 KiB
Diff
From 1cc26aac30b883244e300d872fa3a19f39afbb66 Mon Sep 17 00:00:00 2001
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From: Fabiano Rosas <farosas@suse.de>
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Date: Mon, 18 Sep 2023 14:28:17 -0300
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Subject: [PATCH 03/13] migration: Fix possible races when shutting down the
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return path
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Peter Xu <peterx@redhat.com>
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RH-MergeRequest: 203: migration: Fix race that dest preempt thread close too early
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RH-Jira: RHEL-11219
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: Leonardo Brás <leobras@redhat.com>
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RH-Commit: [3/8] d734387cf07e956a1f1e817c200e5b36cf0a00b1 (peterx/qemu-kvm)
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We cannot call qemu_file_shutdown() on the return path file without
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taking the file lock. The return path thread could be running it's
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cleanup code and have just cleared the from_dst_file pointer.
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Checking ms->to_dst_file for errors could also race with
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migrate_fd_cleanup() which clears the to_dst_file pointer.
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Protect both accesses by taking the file lock.
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This was caught by inspection, it should be rare, but the next patches
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will start calling this code from other places, so let's do the
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correct thing.
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Reviewed-by: Peter Xu <peterx@redhat.com>
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Signed-off-by: Fabiano Rosas <farosas@suse.de>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Message-ID: <20230918172822.19052-4-farosas@suse.de>
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(cherry picked from commit 639decf529793fc544c8055b82be8abe77fa48fa)
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Signed-off-by: Peter Xu <peterx@redhat.com>
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---
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migration/migration.c | 19 ++++++++++---------
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1 file changed, 10 insertions(+), 9 deletions(-)
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diff --git a/migration/migration.c b/migration/migration.c
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index b92c6ae436..517b3e04d2 100644
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--- a/migration/migration.c
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+++ b/migration/migration.c
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@@ -2053,17 +2053,18 @@ static int open_return_path_on_source(MigrationState *ms,
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static int await_return_path_close_on_source(MigrationState *ms)
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{
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/*
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- * If this is a normal exit then the destination will send a SHUT and the
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- * rp_thread will exit, however if there's an error we need to cause
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- * it to exit.
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+ * If this is a normal exit then the destination will send a SHUT
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+ * and the rp_thread will exit, however if there's an error we
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+ * need to cause it to exit. shutdown(2), if we have it, will
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+ * cause it to unblock if it's stuck waiting for the destination.
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*/
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- if (qemu_file_get_error(ms->to_dst_file) && ms->rp_state.from_dst_file) {
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- /*
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- * shutdown(2), if we have it, will cause it to unblock if it's stuck
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- * waiting for the destination.
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- */
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- qemu_file_shutdown(ms->rp_state.from_dst_file);
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+ WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) {
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+ if (ms->to_dst_file && ms->rp_state.from_dst_file &&
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+ qemu_file_get_error(ms->to_dst_file)) {
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+ qemu_file_shutdown(ms->rp_state.from_dst_file);
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+ }
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}
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+
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trace_await_return_path_close_on_source_joining();
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qemu_thread_join(&ms->rp_state.rp_thread);
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ms->rp_state.rp_thread_created = false;
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--
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2.39.3
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