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Message-Id: <1189638236.27182.12.camel@w-sridhar2.beaverton.ibm.com>
Date: Wed, 12 Sep 2007 16:03:55 -0700
From: Sridhar Samudrala <sri@...ibm.com>
To: Vlad Yasevich <vladislav.yasevich@...com>
Cc: netdev@...r.kernel.org, lksctp-developers@...ts.sourceforge.net
Subject: Re: [RFC v2 PATCH 1/2] SCTP: Add RCU synchronization around
sctp_localaddr_list
Vlad,
few minor comments inline.
otherwise, looks good.
Thanks
Sridhar
On Wed, 2007-09-12 at 15:46 -0400, Vlad Yasevich wrote:
> sctp_localaddr_list is modified dynamically via NETDEV_UP
> and NETDEV_DOWN events, but there is not synchronization
> between writer (even handler) and readers. As a result,
> the readers can access an entry that has been freed and
> crash the sytem.
>
> Signed-off-by: Vlad Yasevich <vladislav.yasevich@...com>
> ---
> include/net/sctp/sctp.h | 1 +
> include/net/sctp/structs.h | 6 +++++
> net/sctp/bind_addr.c | 2 +
> net/sctp/ipv6.c | 34 ++++++++++++++++++++++---------
> net/sctp/protocol.c | 46 ++++++++++++++++++++++++++++++-------------
> net/sctp/socket.c | 38 +++++++++++++++++++++++------------
> 6 files changed, 90 insertions(+), 37 deletions(-)
>
> diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
> index d529045..c9cc00c 100644
> --- a/include/net/sctp/sctp.h
> +++ b/include/net/sctp/sctp.h
> @@ -123,6 +123,7 @@
> * sctp/protocol.c
> */
> extern struct sock *sctp_get_ctl_sock(void);
> +extern void sctp_local_addr_free(struct rcu_head *head);
> extern int sctp_copy_local_addr_list(struct sctp_bind_addr *,
> sctp_scope_t, gfp_t gfp,
> int flags);
> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> index c0d5848..a89e361 100644
> --- a/include/net/sctp/structs.h
> +++ b/include/net/sctp/structs.h
> @@ -207,6 +207,9 @@ extern struct sctp_globals {
> * It is a list of sctp_sockaddr_entry.
> */
> struct list_head local_addr_list;
> +
> + /* Lock that protects the local_addr_list writers */
> + spinlock_t addr_list_lock;
>
> /* Flag to indicate if addip is enabled. */
> int addip_enable;
> @@ -242,6 +245,7 @@ extern struct sctp_globals {
> #define sctp_port_alloc_lock (sctp_globals.port_alloc_lock)
> #define sctp_port_hashtable (sctp_globals.port_hashtable)
> #define sctp_local_addr_list (sctp_globals.local_addr_list)
> +#define sctp_local_addr_lock (sctp_globals.addr_list_lock)
> #define sctp_addip_enable (sctp_globals.addip_enable)
> #define sctp_prsctp_enable (sctp_globals.prsctp_enable)
>
> @@ -737,8 +741,10 @@ const union sctp_addr *sctp_source(const struct sctp_chunk *chunk);
> /* This is a structure for holding either an IPv6 or an IPv4 address. */
> struct sctp_sockaddr_entry {
> struct list_head list;
> + struct rcu_head rcu;
> union sctp_addr a;
> __u8 use_as_src;
> + __u8 valid;
> };
>
> typedef struct sctp_chunk *(sctp_packet_phandler_t)(struct sctp_association *);
> diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
> index fdb287a..7fc369f 100644
> --- a/net/sctp/bind_addr.c
> +++ b/net/sctp/bind_addr.c
> @@ -163,8 +163,10 @@ int sctp_add_bind_addr(struct sctp_bind_addr *bp, union sctp_addr *new,
> addr->a.v4.sin_port = htons(bp->port);
>
> addr->use_as_src = use_as_src;
> + addr->valid = 1;
>
> INIT_LIST_HEAD(&addr->list);
> + INIT_RCU_HEAD(&addr->rcu);
> list_add_tail(&addr->list, &bp->address_list);
> SCTP_DBG_OBJCNT_INC(addr);
>
> diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
> index f8aa23d..54ff472 100644
> --- a/net/sctp/ipv6.c
> +++ b/net/sctp/ipv6.c
> @@ -77,13 +77,18 @@
>
> #include <asm/uaccess.h>
>
> -/* Event handler for inet6 address addition/deletion events. */
> +/* Event handler for inet6 address addition/deletion events.
> + * This even is part of the atomic notifier call chain
> + * and thus happens atomically and can NOT sleep. As a result
> + * we can't and really don't need to add any locks to guard the
> + * RCU.
> + */
Now that we are adding a spin_lock, the above comment is not valid.
It should be fixed saying that we still need a lock because we use the
same list for both inet and inet6 address events and they can happen in
parallel.
> static int sctp_inet6addr_event(struct notifier_block *this, unsigned long ev,
> void *ptr)
> {
> struct inet6_ifaddr *ifa = (struct inet6_ifaddr *)ptr;
> - struct sctp_sockaddr_entry *addr;
> - struct list_head *pos, *temp;
> + struct sctp_sockaddr_entry *addr = NULL;
> + struct sctp_sockaddr_entry *temp;
>
> switch (ev) {
> case NETDEV_UP:
> @@ -94,19 +99,26 @@ static int sctp_inet6addr_event(struct notifier_block *this, unsigned long ev,
> memcpy(&addr->a.v6.sin6_addr, &ifa->addr,
> sizeof(struct in6_addr));
> addr->a.v6.sin6_scope_id = ifa->idev->dev->ifindex;
> - list_add_tail(&addr->list, &sctp_local_addr_list);
> + addr->valid = 1;
> + spin_lock_bh(&sctp_local_addr_lock);
> + list_add_tail_rcu(&addr->list, &sctp_local_addr_list);
> + spin_unlock_bh(&sctp_local_addr_lock);
> }
> break;
> case NETDEV_DOWN:
> - list_for_each_safe(pos, temp, &sctp_local_addr_list) {
> - addr = list_entry(pos, struct sctp_sockaddr_entry, list);
> - if (ipv6_addr_equal(&addr->a.v6.sin6_addr, &ifa->addr)) {
> - list_del(pos);
> - kfree(addr);
> + spin_lock_bh(&sctp_local_addr_lock);
> + list_for_each_entry_safe(addr, temp,
> + &sctp_local_addr_list, list) {
> + if (ipv6_addr_equal(&addr->a.v6.sin6_addr,
> + &ifa->addr)) {
> + addr->valid = 0;
> + list_del_rcu(&addr->list);
> break;
> }
> }
> -
> + spin_unlock_bh(&sctp_local_addr_lock);
> + if (addr && !addr->valid)
> + call_rcu(&addr->rcu, sctp_local_addr_free);
> break;
> }
>
> @@ -367,7 +379,9 @@ static void sctp_v6_copy_addrlist(struct list_head *addrlist,
> addr->a.v6.sin6_port = 0;
> addr->a.v6.sin6_addr = ifp->addr;
> addr->a.v6.sin6_scope_id = dev->ifindex;
> + addr->valid = 1;
> INIT_LIST_HEAD(&addr->list);
> + INIT_RCU_HEAD(&addr->rcu);
> list_add_tail(&addr->list, addrlist);
> }
> }
> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
> index e98579b..4688559 100644
> --- a/net/sctp/protocol.c
> +++ b/net/sctp/protocol.c
> @@ -153,6 +153,8 @@ static void sctp_v4_copy_addrlist(struct list_head *addrlist,
> addr->a.v4.sin_family = AF_INET;
> addr->a.v4.sin_port = 0;
> addr->a.v4.sin_addr.s_addr = ifa->ifa_local;
> + addr->valid = 1;
> + INIT_RCU_HEAD(&addr->rcu);
This has nothing to do with this patch, but i noticed that
INIT_LIST_HEAD(&addr->list) is missing here when comparing with
earlier v6 version of this routine.
> list_add_tail(&addr->list, addrlist);
> }
> }
> @@ -192,16 +194,24 @@ static void sctp_free_local_addr_list(void)
> }
> }
>
> +void sctp_local_addr_free(struct rcu_head *head)
> +{
> + struct sctp_sockaddr_entry *e = container_of(head,
> + struct sctp_sockaddr_entry, rcu);
> + kfree(e);
> +}
> +
> /* Copy the local addresses which are valid for 'scope' into 'bp'. */
> int sctp_copy_local_addr_list(struct sctp_bind_addr *bp, sctp_scope_t scope,
> gfp_t gfp, int copy_flags)
> {
> struct sctp_sockaddr_entry *addr;
> int error = 0;
> - struct list_head *pos, *temp;
>
> - list_for_each_safe(pos, temp, &sctp_local_addr_list) {
> - addr = list_entry(pos, struct sctp_sockaddr_entry, list);
> + rcu_read_lock();
> + list_for_each_entry_rcu(addr, &sctp_local_addr_list, list) {
> + if (!addr->valid)
> + continue;
> if (sctp_in_scope(&addr->a, scope)) {
> /* Now that the address is in scope, check to see if
> * the address type is really supported by the local
> @@ -221,6 +231,7 @@ int sctp_copy_local_addr_list(struct sctp_bind_addr *bp, sctp_scope_t scope,
> }
>
> end_copy:
> + rcu_read_unlock();
> return error;
> }
>
> @@ -605,8 +616,8 @@ static int sctp_inetaddr_event(struct notifier_block *this, unsigned long ev,
> void *ptr)
> {
> struct in_ifaddr *ifa = (struct in_ifaddr *)ptr;
> - struct sctp_sockaddr_entry *addr;
> - struct list_head *pos, *temp;
> + struct sctp_sockaddr_entry *addr = NULL;
> + struct sctp_sockaddr_entry *temp;
>
> switch (ev) {
> case NETDEV_UP:
> @@ -615,19 +626,25 @@ static int sctp_inetaddr_event(struct notifier_block *this, unsigned long ev,
> addr->a.v4.sin_family = AF_INET;
> addr->a.v4.sin_port = 0;
> addr->a.v4.sin_addr.s_addr = ifa->ifa_local;
> - list_add_tail(&addr->list, &sctp_local_addr_list);
> + addr->valid = 1;
> + spin_lock_bh(&sctp_local_addr_lock);
> + list_add_tail_rcu(&addr->list, &sctp_local_addr_list);
> + spin_unlock_bh(&sctp_local_addr_lock);
> }
> break;
> case NETDEV_DOWN:
> - list_for_each_safe(pos, temp, &sctp_local_addr_list) {
> - addr = list_entry(pos, struct sctp_sockaddr_entry, list);
> + spin_lock_bh(&sctp_local_addr_lock);
> + list_for_each_entry_safe(addr, temp,
> + &sctp_local_addr_list, list) {
> if (addr->a.v4.sin_addr.s_addr == ifa->ifa_local) {
> - list_del(pos);
> - kfree(addr);
> + addr->valid = 0;
> + list_del_rcu(&addr->list);
> break;
> }
> }
> -
> + spin_unlock_bh(&sctp_local_addr_lock);
> + if (addr && !addr->valid)
> + call_rcu(&addr->rcu, sctp_local_addr_free);
> break;
> }
>
> @@ -1160,6 +1177,7 @@ SCTP_STATIC __init int sctp_init(void)
>
> /* Initialize the local address list. */
> INIT_LIST_HEAD(&sctp_local_addr_list);
> + spin_lock_init(&sctp_local_addr_lock);
> sctp_get_local_addr_list();
>
> /* Register notifier for inet address additions/deletions. */
> @@ -1227,6 +1245,9 @@ SCTP_STATIC __exit void sctp_exit(void)
> sctp_v6_del_protocol();
> inet_del_protocol(&sctp_protocol, IPPROTO_SCTP);
>
> + /* Unregister notifier for inet address additions/deletions. */
> + unregister_inetaddr_notifier(&sctp_inetaddr_notifier);
> +
> /* Free the local address list. */
> sctp_free_local_addr_list();
>
> @@ -1240,9 +1261,6 @@ SCTP_STATIC __exit void sctp_exit(void)
> inet_unregister_protosw(&sctp_stream_protosw);
> inet_unregister_protosw(&sctp_seqpacket_protosw);
>
> - /* Unregister notifier for inet address additions/deletions. */
> - unregister_inetaddr_notifier(&sctp_inetaddr_notifier);
> -
> sctp_sysctl_unregister();
> list_del(&sctp_ipv4_specific.list);
>
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 3335460..a3acf78 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -4057,9 +4057,9 @@ static int sctp_getsockopt_local_addrs_num_old(struct sock *sk, int len,
> int __user *optlen)
> {
> sctp_assoc_t id;
> + struct list_head *pos;
> struct sctp_bind_addr *bp;
> struct sctp_association *asoc;
> - struct list_head *pos, *temp;
> struct sctp_sockaddr_entry *addr;
> rwlock_t *addr_lock;
> int cnt = 0;
> @@ -4096,15 +4096,19 @@ static int sctp_getsockopt_local_addrs_num_old(struct sock *sk, int len,
> addr = list_entry(bp->address_list.next,
> struct sctp_sockaddr_entry, list);
> if (sctp_is_any(&addr->a)) {
> - list_for_each_safe(pos, temp, &sctp_local_addr_list) {
> - addr = list_entry(pos,
> - struct sctp_sockaddr_entry,
> - list);
> + rcu_read_lock();
> + list_for_each_entry_rcu(addr,
> + &sctp_local_addr_list, list) {
> + if (!addr->valid)
> + continue;
> +
> if ((PF_INET == sk->sk_family) &&
> (AF_INET6 == addr->a.sa.sa_family))
> continue;
> +
> cnt++;
> }
> + rcu_read_unlock();
> } else {
> cnt = 1;
> }
> @@ -4127,14 +4131,16 @@ static int sctp_copy_laddrs_old(struct sock *sk, __u16 port,
> int max_addrs, void *to,
> int *bytes_copied)
> {
> - struct list_head *pos, *next;
> struct sctp_sockaddr_entry *addr;
> union sctp_addr temp;
> int cnt = 0;
> int addrlen;
>
> - list_for_each_safe(pos, next, &sctp_local_addr_list) {
> - addr = list_entry(pos, struct sctp_sockaddr_entry, list);
> + rcu_read_lock();
> + list_for_each_entry_rcu(addr, &sctp_local_addr_list, list) {
> + if (!addr->valid)
> + continue;
> +
> if ((PF_INET == sk->sk_family) &&
> (AF_INET6 == addr->a.sa.sa_family))
> continue;
> @@ -4149,6 +4155,7 @@ static int sctp_copy_laddrs_old(struct sock *sk, __u16 port,
> cnt ++;
> if (cnt >= max_addrs) break;
> }
> + rcu_read_unlock();
>
> return cnt;
> }
> @@ -4156,14 +4163,16 @@ static int sctp_copy_laddrs_old(struct sock *sk, __u16 port,
> static int sctp_copy_laddrs(struct sock *sk, __u16 port, void *to,
> size_t space_left, int *bytes_copied)
> {
> - struct list_head *pos, *next;
> struct sctp_sockaddr_entry *addr;
> union sctp_addr temp;
> int cnt = 0;
> int addrlen;
>
> - list_for_each_safe(pos, next, &sctp_local_addr_list) {
> - addr = list_entry(pos, struct sctp_sockaddr_entry, list);
> + rcu_read_lock();
> + list_for_each_entry_rcu(addr, &sctp_local_addr_list, list) {
> + if (!addr->valid)
> + continue;
> +
> if ((PF_INET == sk->sk_family) &&
> (AF_INET6 == addr->a.sa.sa_family))
> continue;
> @@ -4171,8 +4180,10 @@ static int sctp_copy_laddrs(struct sock *sk, __u16 port, void *to,
> sctp_get_pf_specific(sk->sk_family)->addr_v4map(sctp_sk(sk),
> &temp);
> addrlen = sctp_get_af_specific(temp.sa.sa_family)->sockaddr_len;
> - if (space_left < addrlen)
> - return -ENOMEM;
> + if (space_left < addrlen) {
> + cnt = -ENOMEM;
> + break;
> + }
> memcpy(to, &temp, addrlen);
>
> to += addrlen;
> @@ -4180,6 +4191,7 @@ static int sctp_copy_laddrs(struct sock *sk, __u16 port, void *to,
> space_left -= addrlen;
> *bytes_copied += addrlen;
> }
> + rcu_read_unlock();
>
> return cnt;
> }
-
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