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[PATCH 3/8] migration: Fix possible races when shutting down the return
From: |
Fabiano Rosas |
Subject: |
[PATCH 3/8] migration: Fix possible races when shutting down the return path |
Date: |
Mon, 18 Sep 2023 14:28:17 -0300 |
We cannot call qemu_file_shutdown() on the return path file without
taking the file lock. The return path thread could be running it's
cleanup code and have just cleared the from_dst_file pointer.
Checking ms->to_dst_file for errors could also race with
migrate_fd_cleanup() which clears the to_dst_file pointer.
Protect both accesses by taking the file lock.
This was caught by inspection, it should be rare, but the next patches
will start calling this code from other places, so let's do the
correct thing.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
migration/migration.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/migration/migration.c b/migration/migration.c
index d426b69ada..15b7258bb2 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2064,17 +2064,18 @@ static int open_return_path_on_source(MigrationState
*ms,
static int await_return_path_close_on_source(MigrationState *ms)
{
/*
- * If this is a normal exit then the destination will send a SHUT and the
- * rp_thread will exit, however if there's an error we need to cause
- * it to exit.
+ * If this is a normal exit then the destination will send a SHUT
+ * and the rp_thread will exit, however if there's an error we
+ * need to cause it to exit. shutdown(2), if we have it, will
+ * cause it to unblock if it's stuck waiting for the destination.
*/
- if (qemu_file_get_error(ms->to_dst_file) && ms->rp_state.from_dst_file) {
- /*
- * shutdown(2), if we have it, will cause it to unblock if it's stuck
- * waiting for the destination.
- */
- qemu_file_shutdown(ms->rp_state.from_dst_file);
+ WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) {
+ if (ms->to_dst_file && ms->rp_state.from_dst_file &&
+ qemu_file_get_error(ms->to_dst_file)) {
+ qemu_file_shutdown(ms->rp_state.from_dst_file);
+ }
}
+
trace_await_return_path_close_on_source_joining();
qemu_thread_join(&ms->rp_state.rp_thread);
ms->rp_state.rp_thread_created = false;
--
2.35.3
- [PATCH 0/8] migration fixes, Fabiano Rosas, 2023/09/18
- [PATCH 1/8] migration: Fix race that dest preempt thread close too early, Fabiano Rosas, 2023/09/18
- [PATCH 4/8] migration: Fix possible race when shutting down to_dst_file, Fabiano Rosas, 2023/09/18
- [PATCH 2/8] migration: Fix possible race when setting rp_state.error, Fabiano Rosas, 2023/09/18
- [PATCH 3/8] migration: Fix possible races when shutting down the return path,
Fabiano Rosas <=
- [PATCH 5/8] migration: Remove redundant cleanup of postcopy_qemufile_src, Fabiano Rosas, 2023/09/18
- [PATCH 6/8] migration: Consolidate return path closing code, Fabiano Rosas, 2023/09/18
- [PATCH 7/8] migration: Replace the return path retry logic, Fabiano Rosas, 2023/09/18
- [PATCH 8/8] migration: Move return path cleanup to main migration thread, Fabiano Rosas, 2023/09/18
- Re: [PATCH 0/8] migration fixes, Fabiano Rosas, 2023/09/27
- Re: [PATCH 0/8] migration fixes, Stefan Hajnoczi, 2023/09/27
- Re: [PATCH 0/8] migration fixes, Stefan Hajnoczi, 2023/09/27