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network: Introduce mutex for bridge name generation

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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.

Resolves: https://gitlab.com/libvirt/libvirt/-/issues/78
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>
This commit is contained in:
Michal Privoznik 2021-01-07 15:51:02 +01:00
parent 225b363d50
commit ea0cfa1153
1 changed files with 11 additions and 2 deletions
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13
src/network/bridge_driver.c
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@ -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;
}