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[Qemu-stable] [PATCH 135/156] aio: fix qemu_bh_schedule() bh->ctx race c
From: |
Michael Roth |
Subject: |
[Qemu-stable] [PATCH 135/156] aio: fix qemu_bh_schedule() bh->ctx race condition |
Date: |
Tue, 8 Jul 2014 12:18:46 -0500 |
From: Stefan Hajnoczi <address@hidden>
qemu_bh_schedule() is supposed to be thread-safe at least the first time
it is called. Unfortunately this is not quite true:
bh->scheduled = 1;
aio_notify(bh->ctx);
Since another thread may run the BH callback once it has been scheduled,
there is a race condition if the callback frees the BH before
aio_notify(bh->ctx) has a chance to run.
Reported-by: Stefan Priebe <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
Reviewed-by: Paolo Bonzini <address@hidden>
Tested-by: Stefan Priebe <address@hidden>
(cherry picked from commit 924fe1293c3e7a3c787bbdfb351e7f168caee3e9)
Signed-off-by: Michael Roth <address@hidden>
---
async.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/async.c b/async.c
index 5fb3fa6..c6d810d 100644
--- a/async.c
+++ b/async.c
@@ -117,15 +117,21 @@ void qemu_bh_schedule_idle(QEMUBH *bh)
void qemu_bh_schedule(QEMUBH *bh)
{
+ AioContext *ctx;
+
if (bh->scheduled)
return;
+ ctx = bh->ctx;
bh->idle = 0;
- /* Make sure that idle & any writes needed by the callback are done
- * before the locations are read in the aio_bh_poll.
+ /* Make sure that:
+ * 1. idle & any writes needed by the callback are done before the
+ * locations are read in the aio_bh_poll.
+ * 2. ctx is loaded before scheduled is set and the callback has a chance
+ * to execute.
*/
- smp_wmb();
+ smp_mb();
bh->scheduled = 1;
- aio_notify(bh->ctx);
+ aio_notify(ctx);
}
--
1.9.1
- [Qemu-stable] [PATCH 019/156] ide: Correct improper smart self test counter reset in ide core., (continued)
- [Qemu-stable] [PATCH 019/156] ide: Correct improper smart self test counter reset in ide core., Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 083/156] vpc: Validate block size (CVE-2014-0142), Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 111/156] qcow2: Fix copy_sectors() with VM state, Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 103/156] dmg: prevent out-of-bounds array access on terminator, Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 149/156] nbd: Don't validate from and len in NBD_CMD_DISC., Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 058/156] stellaris_enet: block migration, Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 017/156] qcow2: Flush metadata during read-only reopen, Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 057/156] virtio: validate config_len on load, Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 106/156] dmg: sanitize chunk length and sectorcount (CVE-2014-0145), Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 082/156] vpc/vhd: add bounds check for max_table_entries and block_size (CVE-2014-0144), Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 135/156] aio: fix qemu_bh_schedule() bh->ctx race condition,
Michael Roth <=
- [Qemu-stable] [PATCH 105/156] dmg: use appropriate types when reading chunks, Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 070/156] qemu-iotests: add cloop input validation tests, Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 067/156] migration: remove duplicate code, Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 012/156] mirror: fix throttling delay calculation, Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 078/156] bochs: Use unsigned variables for offsets and sizes (CVE-2014-0147), Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 014/156] virtio-net: Do not filter VLANs without F_CTRL_VLAN, Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 138/156] qga: Fix handle fd leak in acquire_privilege(), Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 050/156] ssd0323: fix buffer overun on invalid state load, Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 080/156] bochs: Check extent_size header field (CVE-2014-0142), Michael Roth, 2014/07/08
- [Qemu-stable] [PATCH 119/156] qcow1: Validate image size (CVE-2014-0223), Michael Roth, 2014/07/09