When defining/creating a network the bridge name may be filled in automatically by libvirt (if none provided in the input XML or the one provided is a pattern, e.g. "virbr%d"). During the bridge name generation process a candidate name is generated which is then checked with the rest of already defined/running networks for collisions. Problem is, that there is no mutex guarding this critical section and thus if two threads line up so that they both generate the same candidate they won't find any collision and the same name is then stored. Closes: https://gitlab.com/libvirt/libvirt/-/issues/78 Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx> --- src/network/bridge_driver.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c index a7c5aade14..b7c604eaea 100644 --- a/src/network/bridge_driver.c +++ b/src/network/bridge_driver.c @@ -74,6 +74,8 @@ #define VIR_FROM_THIS VIR_FROM_NETWORK #define MAX_BRIDGE_ID 256 +static virMutex bridgeNameValidateMutex = VIR_MUTEX_INITIALIZER; + /** * VIR_NETWORK_DHCP_LEASE_FILE_SIZE_MAX: * @@ -3115,20 +3117,27 @@ static int networkBridgeNameValidate(virNetworkObjListPtr nets, virNetworkDefPtr def) { + virMutexLock(&bridgeNameValidateMutex); + if (def->bridge && !strstr(def->bridge, "%d")) { if (virNetworkObjBridgeInUse(nets, def->bridge, def->name)) { virReportError(VIR_ERR_INTERNAL_ERROR, _("bridge name '%s' already in use."), def->bridge); - return -1; + goto error; } } else { /* Allocate a bridge name */ if (networkFindUnusedBridgeName(nets, def) < 0) - return -1; + goto error; } + virMutexUnlock(&bridgeNameValidateMutex); return 0; + + error: + virMutexUnlock(&bridgeNameValidateMutex); + return -1; } -- 2.26.2
