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![David Howells](/assets/img/avatar_default.png)
The refcounting on afs_cb_interest struct objects in
afs_register_server_cb_interest() is wrong as it uses the server list
entry's call back interest pointer without regard for the fact that it
might be replaced at any time and the object thrown away.
Fix this by:
(1) Put a lock on the afs_server_list struct that can be used to
mediate access to the callback interest pointers in the servers array.
(2) Keep a ref on the callback interest that we get from the entry.
(3) Dropping the old reference held by vnode->cb_interest if we replace
the pointer.
Fixes: c435ee3455
("afs: Overhaul the callback handling")
Signed-off-by: David Howells <dhowells@redhat.com>
157 lines
3.6 KiB
C
157 lines
3.6 KiB
C
/* AFS fileserver list management.
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*
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* Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include "internal.h"
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void afs_put_serverlist(struct afs_net *net, struct afs_server_list *slist)
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{
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int i;
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if (slist && refcount_dec_and_test(&slist->usage)) {
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for (i = 0; i < slist->nr_servers; i++) {
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afs_put_cb_interest(net, slist->servers[i].cb_interest);
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afs_put_server(net, slist->servers[i].server);
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}
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kfree(slist);
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}
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}
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/*
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* Build a server list from a VLDB record.
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*/
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struct afs_server_list *afs_alloc_server_list(struct afs_cell *cell,
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struct key *key,
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struct afs_vldb_entry *vldb,
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u8 type_mask)
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{
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struct afs_server_list *slist;
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struct afs_server *server;
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int ret = -ENOMEM, nr_servers = 0, i, j;
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for (i = 0; i < vldb->nr_servers; i++)
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if (vldb->fs_mask[i] & type_mask)
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nr_servers++;
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slist = kzalloc(sizeof(struct afs_server_list) +
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sizeof(struct afs_server_entry) * nr_servers,
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GFP_KERNEL);
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if (!slist)
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goto error;
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refcount_set(&slist->usage, 1);
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rwlock_init(&slist->lock);
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/* Make sure a records exists for each server in the list. */
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for (i = 0; i < vldb->nr_servers; i++) {
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if (!(vldb->fs_mask[i] & type_mask))
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continue;
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server = afs_lookup_server(cell, key, &vldb->fs_server[i]);
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if (IS_ERR(server)) {
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ret = PTR_ERR(server);
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if (ret == -ENOENT ||
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ret == -ENOMEDIUM)
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continue;
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goto error_2;
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}
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/* Insertion-sort by UUID */
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for (j = 0; j < slist->nr_servers; j++)
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if (memcmp(&slist->servers[j].server->uuid,
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&server->uuid,
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sizeof(server->uuid)) >= 0)
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break;
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if (j < slist->nr_servers) {
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if (slist->servers[j].server == server) {
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afs_put_server(cell->net, server);
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continue;
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}
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memmove(slist->servers + j + 1,
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slist->servers + j,
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(slist->nr_servers - j) * sizeof(struct afs_server_entry));
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}
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slist->servers[j].server = server;
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slist->nr_servers++;
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}
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if (slist->nr_servers == 0) {
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ret = -EDESTADDRREQ;
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goto error_2;
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}
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return slist;
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error_2:
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afs_put_serverlist(cell->net, slist);
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error:
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return ERR_PTR(ret);
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}
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/*
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* Copy the annotations from an old server list to its potential replacement.
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*/
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bool afs_annotate_server_list(struct afs_server_list *new,
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struct afs_server_list *old)
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{
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struct afs_server *cur;
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int i, j;
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if (old->nr_servers != new->nr_servers)
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goto changed;
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for (i = 0; i < old->nr_servers; i++)
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if (old->servers[i].server != new->servers[i].server)
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goto changed;
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return false;
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changed:
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/* Maintain the same current server as before if possible. */
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cur = old->servers[old->index].server;
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for (j = 0; j < new->nr_servers; j++) {
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if (new->servers[j].server == cur) {
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new->index = j;
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break;
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}
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}
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/* Keep the old callback interest records where possible so that we
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* maintain callback interception.
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*/
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i = 0;
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j = 0;
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while (i < old->nr_servers && j < new->nr_servers) {
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if (new->servers[j].server == old->servers[i].server) {
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struct afs_cb_interest *cbi = old->servers[i].cb_interest;
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if (cbi) {
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new->servers[j].cb_interest = cbi;
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refcount_inc(&cbi->usage);
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}
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i++;
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j++;
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continue;
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}
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if (new->servers[j].server < old->servers[i].server) {
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j++;
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continue;
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}
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i++;
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continue;
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}
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return true;
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}
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