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author | Jeremy Kerr <jk@codeconstruct.com.au> | 2021-09-29 15:26:07 +0800 |
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committer | David S. Miller <davem@davemloft.net> | 2021-09-29 11:00:11 +0100 |
commit | 73c618456dc5cf2acb597256d633060cf75de8d6 (patch) | |
tree | a9efbe38933f94dae310553d398ccb2989acc554 /include/net/mctp.h | |
parent | 1f6c77ac9e6ecef152fd5df94c4b3c346adb197a (diff) | |
download | linux-stable-73c618456dc5cf2acb597256d633060cf75de8d6.tar.gz linux-stable-73c618456dc5cf2acb597256d633060cf75de8d6.tar.bz2 linux-stable-73c618456dc5cf2acb597256d633060cf75de8d6.zip |
mctp: locking, lifetime and validity changes for sk_keys
We will want to invalidate sk_keys in a future change, which will
require a boolean flag to mark invalidated items in the socket & net
namespace lists. We'll also need to take a reference to keys, held over
non-atomic contexts, so we need a refcount on keys also.
This change adds a validity flag (currently always true) and refcount to
struct mctp_sk_key. With a refcount on the keys, using RCU no longer
makes much sense; we have exact indications on the lifetime of keys. So,
we also change the RCU list traversal to a locked implementation.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/mctp.h')
-rw-r--r-- | include/net/mctp.h | 46 |
1 files changed, 31 insertions, 15 deletions
diff --git a/include/net/mctp.h b/include/net/mctp.h index a824d47c3c6d..bf783dc3ea45 100644 --- a/include/net/mctp.h +++ b/include/net/mctp.h @@ -67,30 +67,36 @@ struct mctp_sock { /* Key for matching incoming packets to sockets or reassembly contexts. * Packets are matched on (src,dest,tag). * - * Lifetime requirements: + * Lifetime / locking requirements: * - * - keys are free()ed via RCU + * - individual key data (ie, the struct itself) is protected by key->lock; + * changes must be made with that lock held. + * + * - the lookup fields: peer_addr, local_addr and tag are set before the + * key is added to lookup lists, and never updated. + * + * - A ref to the key must be held (throuh key->refs) if a pointer to the + * key is to be accessed after key->lock is released. * * - a mctp_sk_key contains a reference to a struct sock; this is valid * for the life of the key. On sock destruction (through unhash), the key is - * removed from lists (see below), and will not be observable after a RCU - * grace period. - * - * any RX occurring within that grace period may still queue to the socket, - * but will hit the SOCK_DEAD case before the socket is freed. + * removed from lists (see below), and marked invalid. * * - these mctp_sk_keys appear on two lists: * 1) the struct mctp_sock->keys list * 2) the struct netns_mctp->keys list * - * updates to either list are performed under the netns_mctp->keys - * lock. + * presences on these lists requires a (single) refcount to be held; both + * lists are updated as a single operation. + * + * Updates and lookups in either list are performed under the + * netns_mctp->keys lock. Lookup functions will need to lock the key and + * take a reference before unlocking the keys_lock. Consequently, the list's + * keys_lock *cannot* be acquired with the individual key->lock held. * * - a key may have a sk_buff attached as part of an in-progress message - * reassembly (->reasm_head). The reassembly context is protected by - * reasm_lock, which may be acquired with the keys lock (above) held, if - * necessary. Consequently, keys lock *cannot* be acquired with the - * reasm_lock held. + * reassembly (->reasm_head). The reasm data is protected by the individual + * key->lock. * * - there are two destruction paths for a mctp_sk_key: * @@ -116,14 +122,22 @@ struct mctp_sk_key { /* per-socket list */ struct hlist_node sklist; + /* lock protects against concurrent updates to the reassembly and + * expiry data below. + */ + spinlock_t lock; + + /* Keys are referenced during the output path, which may sleep */ + refcount_t refs; + /* incoming fragment reassembly context */ - spinlock_t reasm_lock; struct sk_buff *reasm_head; struct sk_buff **reasm_tailp; bool reasm_dead; u8 last_seq; - struct rcu_head rcu; + /* key validity */ + bool valid; }; struct mctp_skb_cb { @@ -191,6 +205,8 @@ int mctp_do_route(struct mctp_route *rt, struct sk_buff *skb); int mctp_local_output(struct sock *sk, struct mctp_route *rt, struct sk_buff *skb, mctp_eid_t daddr, u8 req_tag); +void mctp_key_unref(struct mctp_sk_key *key); + /* routing <--> device interface */ unsigned int mctp_default_net(struct net *net); int mctp_default_net_set(struct net *net, unsigned int index); |