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xen.27500
xsa326-14.patch
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File xsa326-14.patch of Package xen.27500
From 145c8375f382fe8535d633891cfdb47ec29a490a Mon Sep 17 00:00:00 2001 From: Juergen Gross <jgross@suse.com> Date: Tue, 13 Sep 2022 07:35:10 +0200 Subject: tools/xenstore: add memory accounting for nodes Add the memory accounting for Xenstore nodes. In order to make this not too complicated allow for some sloppiness when writing nodes. Any hard quota violation will result in no further requests to be accepted. This is part of XSA-326 / CVE-2022-42315. Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Julien Grall <jgrall@amazon.com> --- a/tools/xenstore/xenstored_core.c +++ b/tools/xenstore/xenstored_core.c @@ -496,6 +496,117 @@ static void initialize_fds(int sock, int } } +static void get_acc_data(TDB_DATA *key, struct node_account_data *acc) +{ + TDB_DATA old_data; + struct xs_tdb_record_hdr *hdr; + + if (acc->memory < 0) { + old_data = tdb_fetch(tdb_ctx, *key); + /* No check for error, as the node might not exist. */ + if (old_data.dptr == NULL) { + acc->memory = 0; + } else { + hdr = (void *)old_data.dptr; + acc->memory = old_data.dsize; + acc->domid = hdr->perms[0].id; + } + talloc_free(old_data.dptr); + } +} + +/* + * Per-transaction nodes need to be accounted for the transaction owner. + * Those nodes are stored in the data base with the transaction generation + * count prepended (e.g. 123/local/domain/...). So testing for the node's + * key not to start with "/" is sufficient. + */ +static unsigned int get_acc_domid(struct connection *conn, TDB_DATA *key, + unsigned int domid) +{ + return (!conn || key->dptr[0] == '/') ? domid : conn->id; +} + +int do_tdb_write(struct connection *conn, TDB_DATA *key, TDB_DATA *data, + struct node_account_data *acc, bool no_quota_check) +{ + struct xs_tdb_record_hdr *hdr = (void *)data->dptr; + struct node_account_data old_acc = {}; + unsigned int old_domid, new_domid; + int ret; + + if (!acc) + old_acc.memory = -1; + else + old_acc = *acc; + + get_acc_data(key, &old_acc); + old_domid = get_acc_domid(conn, key, old_acc.domid); + new_domid = get_acc_domid(conn, key, hdr->perms[0].id); + + /* + * Don't check for ENOENT, as we want to be able to switch orphaned + * nodes to new owners. + */ + if (old_acc.memory) + domain_memory_add_nochk(old_domid, + -old_acc.memory - key->dsize); + ret = domain_memory_add(new_domid, data->dsize + key->dsize, + no_quota_check); + if (ret) { + /* Error path, so no quota check. */ + if (old_acc.memory) + domain_memory_add_nochk(old_domid, + old_acc.memory + key->dsize); + return ret; + } + + /* TDB should set errno, but doesn't even set ecode AFAICT. */ + if (tdb_store(tdb_ctx, *key, *data, TDB_REPLACE) != 0) { + domain_memory_add_nochk(new_domid, -data->dsize - key->dsize); + /* Error path, so no quota check. */ + if (old_acc.memory) + domain_memory_add_nochk(old_domid, + old_acc.memory + key->dsize); + errno = EIO; + return errno; + } + + if (acc) { + /* Don't use new_domid, as it might be a transaction node. */ + acc->domid = hdr->perms[0].id; + acc->memory = data->dsize; + } + + return 0; +} + +int do_tdb_delete(struct connection *conn, TDB_DATA *key, + struct node_account_data *acc) +{ + struct node_account_data tmp_acc; + unsigned int domid; + + if (!acc) { + acc = &tmp_acc; + acc->memory = -1; + } + + get_acc_data(key, acc); + + if (tdb_delete(tdb_ctx, *key)) { + errno = EIO; + return errno; + } + + if (acc->memory) { + domid = get_acc_domid(conn, key, acc->domid); + domain_memory_add_nochk(domid, -acc->memory - key->dsize); + } + + return 0; +} + /* * If it fails, returns NULL and sets errno. * Temporary memory allocations will be done with ctx. @@ -549,9 +660,15 @@ struct node *read_node(struct connection /* Permissions are struct xs_permissions. */ node->perms.p = hdr->perms; + node->acc.domid = node->perms.p[0].id; + node->acc.memory = data.dsize; if (domain_adjust_node_perms(conn, node)) goto error; + /* If owner is gone reset currently accounted memory size. */ + if (node->acc.domid != node->perms.p[0].id) + node->acc.memory = 0; + /* Data is binary blob (usually ascii, no nul). */ node->data = node->perms.p + hdr->num_perms; /* Children is strings, nul separated. */ @@ -615,12 +732,9 @@ int write_node_raw(struct connection *co p += node->datalen; memcpy(p, node->children, node->childlen); - /* TDB should set errno, but doesn't even set ecode AFAICT. */ - if (tdb_store(tdb_ctx, *key, data, TDB_REPLACE) != 0) { - corrupt(conn, "Write of %s failed", key->dptr); - errno = EIO; - return errno; - } + if (do_tdb_write(conn, key, &data, &node->acc, no_quota_check)) + return EIO; + return 0; } @@ -1119,7 +1233,7 @@ static void delete_node_single(struct co if (access_node(conn, node, NODE_ACCESS_DELETE, &key)) return; - if (tdb_delete(tdb_ctx, key) != 0) { + if (do_tdb_delete(conn, &key, &node->acc) != 0) { corrupt(conn, "Could not delete '%s'", node->name); return; } @@ -1182,6 +1296,7 @@ static struct node *construct_node(struc /* No children, no data */ node->children = node->data = NULL; node->childlen = node->datalen = 0; + node->acc.memory = 0; node->parent = parent; return node; @@ -1190,17 +1305,17 @@ nomem: return NULL; } -static void destroy_node_rm(struct node *node) +static void destroy_node_rm(struct connection *conn, struct node *node) { if (streq(node->name, "/")) corrupt(NULL, "Destroying root node!"); - tdb_delete(tdb_ctx, node->key); + do_tdb_delete(conn, &node->key, &node->acc); } static int destroy_node(struct connection *conn, struct node *node) { - destroy_node_rm(node); + destroy_node_rm(conn, node); domain_entry_dec(conn, node); /* @@ -1252,7 +1367,7 @@ static struct node *create_node(struct c /* Account for new node */ if (i->parent) { if (domain_entry_inc(conn, i)) { - destroy_node_rm(i); + destroy_node_rm(conn, i); return NULL; } } @@ -2079,7 +2194,7 @@ static int clean_store_(TDB_CONTEXT *tdb if (!hashtable_search(reachable, name)) { log("clean_store: '%s' is orphaned!", name); if (recovery) { - tdb_delete(tdb, key); + do_tdb_delete(NULL, &key, NULL); } } --- a/tools/xenstore/xenstored_core.h +++ b/tools/xenstore/xenstored_core.h @@ -143,6 +143,11 @@ struct node_perms { struct xs_permissions *p; }; +struct node_account_data { + unsigned int domid; + int memory; /* -1 if unknown */ +}; + struct node { const char *name; /* Key used to update TDB */ @@ -165,6 +170,9 @@ struct node { /* Children, each nul-terminated. */ unsigned int childlen; char *children; + + /* Allocation information for node currently in store. */ + struct node_account_data acc; }; /* Return the only argument in the input. */ @@ -260,6 +268,11 @@ xengnttab_handle **xgt_handle; int remember_string(struct hashtable *hash, const char *str); +int do_tdb_write(struct connection *conn, TDB_DATA *key, TDB_DATA *data, + struct node_account_data *acc, bool no_quota_check); +int do_tdb_delete(struct connection *conn, TDB_DATA *key, + struct node_account_data *acc); + void conn_free_buffered_data(struct connection *conn); #endif /* _XENSTORED_CORE_H */ --- a/tools/xenstore/xenstored_transaction.c +++ b/tools/xenstore/xenstored_transaction.c @@ -153,6 +153,9 @@ struct transaction /* List of all transactions active on this connection. */ struct list_head list; + /* Connection this transaction is associated with. */ + struct connection *conn; + /* Connection-local identifier for this transaction. */ uint32_t id; @@ -292,6 +295,8 @@ int access_node(struct connection *conn, introduce = true; i->ta_node = false; + /* acc.memory < 0 means "unknown, get size from TDB". */ + node->acc.memory = -1; /* * Additional transaction-specific node for read type. We only @@ -416,11 +421,11 @@ static int finalize_transaction(struct c goto err; hdr = (void *)data.dptr; hdr->generation = ++generation; - ret = tdb_store(tdb_ctx, key, data, - TDB_REPLACE); + ret = do_tdb_write(conn, &key, &data, NULL, + true); talloc_free(data.dptr); } else { - ret = tdb_delete(tdb_ctx, key); + ret = do_tdb_delete(conn, &key, NULL); } if (ret) goto err; @@ -431,7 +436,7 @@ static int finalize_transaction(struct c } } - if (i->ta_node && tdb_delete(tdb_ctx, ta_key)) + if (i->ta_node && do_tdb_delete(conn, &ta_key, NULL)) goto err; list_del(&i->list); talloc_free(i); @@ -459,7 +464,7 @@ static int destroy_transaction(void *_tr i->node); if (trans_name) { set_tdb_key(trans_name, &key); - tdb_delete(tdb_ctx, key); + do_tdb_delete(trans->conn, &key, NULL); } } list_del(&i->list); @@ -503,6 +508,7 @@ int do_transaction_start(struct connecti INIT_LIST_HEAD(&trans->accessed); INIT_LIST_HEAD(&trans->changed_domains); + trans->conn = conn; trans->fail = false; trans->generation = ++generation;
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