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server-ref-list-20040729

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There was a race condition where between a thread calling cm_GetServerList and using the returned server list, another
thread could free the server list.  Now cm_GetServerList duplicates the server list with proper locks held.  Callers of
cm_GetServerList call cm_FreeServerList to free the returned list.
This commit is contained in:
Asanka Herath 2004-07-29 14:53:35 +00:00 committed by Jeffrey Altman
parent 2395eb6075
commit 924fb5f5b9
1 changed files with 36 additions and 2 deletions
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38
src/WINNT/afsd/cm_conn.c
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@ -103,6 +103,7 @@ long cm_GetServerList(struct cm_fid *fidp, struct cm_user *userp,
long code; long code;
cm_volume_t *volp = NULL; cm_volume_t *volp = NULL;
cm_serverRef_t *serversp = NULL; cm_serverRef_t *serversp = NULL;
cm_serverRef_t *newServersp = NULL;
cm_cell_t *cellp = NULL; cm_cell_t *cellp = NULL;
if (!fidp) { if (!fidp) {
@ -116,6 +117,7 @@ long cm_GetServerList(struct cm_fid *fidp, struct cm_user *userp,
code = cm_GetVolumeByID(cellp, fidp->volume, userp, reqp, &volp); code = cm_GetVolumeByID(cellp, fidp->volume, userp, reqp, &volp);
if (code) return code; if (code) return code;
lock_ObtainMutex(&volp->mx);
if (fidp->volume == volp->rwID) if (fidp->volume == volp->rwID)
serversp = volp->rwServersp; serversp = volp->rwServersp;
else if (fidp->volume == volp->roID) else if (fidp->volume == volp->roID)
@ -125,8 +127,36 @@ long cm_GetServerList(struct cm_fid *fidp, struct cm_user *userp,
else else
serversp = NULL; serversp = NULL;
/* make a copy of the server list because by the time the
caller tries to use it, it might have been freed.
Preserve server order. */
if(serversp) {
cm_serverRef_t ** nl;
cm_serverRef_t * tref;
nl = &newServersp;
lock_ObtainWrite(&cm_serverLock);
while(serversp) {
tref = malloc(sizeof(cm_serverRef_t));
tref->next = NULL;
tref->server = serversp->server;
tref->status = serversp->status;
tref->server->refCount++;
*nl = tref;
nl = &tref->next;
serversp = serversp->next;
}
lock_ReleaseWrite(&cm_serverLock);
}
lock_ReleaseMutex(&volp->mx);
cm_PutVolume(volp); cm_PutVolume(volp);
*serverspp = serversp; *serverspp = newServersp;
return 0; return 0;
} }
@ -217,6 +247,7 @@ cm_Analyze(cm_conn_t *connp, cm_user_t *userp, cm_req_t *reqp,
retry = 1; retry = 1;
} }
cm_FreeServerList(&serversp);
if (fidp != NULL) /* Not a VLDB call */ if (fidp != NULL) /* Not a VLDB call */
cm_ForceUpdateVolume(fidp, userp, reqp); cm_ForceUpdateVolume(fidp, userp, reqp);
@ -231,6 +262,7 @@ cm_Analyze(cm_conn_t *connp, cm_user_t *userp, cm_req_t *reqp,
tsrp->status = not_busy; tsrp->status = not_busy;
} }
lock_ReleaseWrite(&cm_serverLock); lock_ReleaseWrite(&cm_serverLock);
cm_FreeServerList(&serversp);
thrd_Sleep(5000); thrd_Sleep(5000);
retry = 1; retry = 1;
} }
@ -247,6 +279,7 @@ cm_Analyze(cm_conn_t *connp, cm_user_t *userp, cm_req_t *reqp,
} }
} }
lock_ReleaseWrite(&cm_serverLock); lock_ReleaseWrite(&cm_serverLock);
cm_FreeServerList(&serversp);
retry = 1; retry = 1;
} }
@ -279,11 +312,11 @@ cm_Analyze(cm_conn_t *connp, cm_user_t *userp, cm_req_t *reqp,
/* Mark server offline for this volume */ /* Mark server offline for this volume */
cm_GetServerList(fidp, userp, reqp, &serversp); cm_GetServerList(fidp, userp, reqp, &serversp);
for (tsrp = serversp; tsrp; tsrp=tsrp->next) { for (tsrp = serversp; tsrp; tsrp=tsrp->next) {
if (tsrp->server == serverp) if (tsrp->server == serverp)
tsrp->status = offline; tsrp->status = offline;
} }
cm_FreeServerList(&serversp);
retry = 1; retry = 1;
} }
@ -556,5 +589,6 @@ long cm_Conn(struct cm_fid *fidp, struct cm_user *userp, cm_req_t *reqp,
} }
code = cm_ConnByMServers(serversp, userp, reqp, connpp); code = cm_ConnByMServers(serversp, userp, reqp, connpp);
cm_FreeServerList(&serversp);
return code; return code;
} }