[PATCH 3.16 60/72] appletalk: Fix potential NULL pointer dereference in unregister_snap_client

3.16.79-rc1 review patch. If anyone has any objections, please let me know.

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From: YueHaibing yuehaibing@huawei.com

commit 9804501fa1228048857910a6bf23e085aade37cc upstream.

register_snap_client may return NULL, all the callers check it, but only print a warning. This will result in NULL pointer dereference in unregister_snap_client and other places.

It has always been used like this since v2.6

Reported-by: Dan Carpenter dan.carpenter@oracle.com Signed-off-by: YueHaibing yuehaibing@huawei.com Signed-off-by: David S. Miller davem@davemloft.net [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- include/linux/atalk.h | 2 +- net/appletalk/aarp.c | 15 ++++++++++++--- net/appletalk/ddp.c | 20 ++++++++++++-------- 3 files changed, 25 insertions(+), 12 deletions(-)

--- a/include/linux/atalk.h +++ b/include/linux/atalk.h @@ -107,7 +107,7 @@ static __inline__ struct elapaarp *aarp_ #define AARP_RESOLVE_TIME (10 * HZ)

extern struct datalink_proto *ddp_dl, *aarp_dl; -extern void aarp_proto_init(void); +extern int aarp_proto_init(void);

/* Inter module exports */

--- a/net/appletalk/aarp.c +++ b/net/appletalk/aarp.c @@ -879,15 +879,24 @@ static struct notifier_block aarp_notifi

static unsigned char aarp_snap_id[] = { 0x00, 0x00, 0x00, 0x80, 0xF3 };

-void __init aarp_proto_init(void) +int __init aarp_proto_init(void) { + int rc; + aarp_dl = register_snap_client(aarp_snap_id, aarp_rcv); - if (!aarp_dl) + if (!aarp_dl) { printk(KERN_CRIT "Unable to register AARP with SNAP.\n"); + return -ENOMEM; + } setup_timer(&aarp_timer, aarp_expire_timeout, 0); aarp_timer.expires = jiffies + sysctl_aarp_expiry_time; add_timer(&aarp_timer); - register_netdevice_notifier(&aarp_notifier); + rc = register_netdevice_notifier(&aarp_notifier); + if (rc) { + del_timer_sync(&aarp_timer); + unregister_snap_client(aarp_dl); + } + return rc; }

/* Remove the AARP entries associated with a device. */ --- a/net/appletalk/ddp.c +++ b/net/appletalk/ddp.c @@ -1912,9 +1912,6 @@ static unsigned char ddp_snap_id[] = { 0 EXPORT_SYMBOL(atrtr_get_dev); EXPORT_SYMBOL(atalk_find_dev_addr);

-static const char atalk_err_snap[] __initconst = - KERN_CRIT "Unable to register DDP with SNAP.\n"; - /* Called by proto.c on kernel start up */ static int __init atalk_init(void) { @@ -1929,17 +1926,22 @@ static int __init atalk_init(void) goto out_proto;

ddp_dl = register_snap_client(ddp_snap_id, atalk_rcv); - if (!ddp_dl) - printk(atalk_err_snap); + if (!ddp_dl) { + pr_crit("Unable to register DDP with SNAP.\n"); + goto out_sock; + }

dev_add_pack(&ltalk_packet_type); dev_add_pack(&ppptalk_packet_type);

rc = register_netdevice_notifier(&ddp_notifier); if (rc) - goto out_sock; + goto out_snap; + + rc = aarp_proto_init(); + if (rc) + goto out_dev;

- aarp_proto_init(); rc = atalk_proc_init(); if (rc) goto out_aarp; @@ -1953,11 +1955,13 @@ out_proc: atalk_proc_exit(); out_aarp: aarp_cleanup_module(); +out_dev: unregister_netdevice_notifier(&ddp_notifier); -out_sock: +out_snap: dev_remove_pack(&ppptalk_packet_type); dev_remove_pack(&ltalk_packet_type); unregister_snap_client(ddp_dl); +out_sock: sock_unregister(PF_APPLETALK); out_proto: proto_unregister(&ddp_proto);