[PATCH v2] sctp: fix incorrect overflow check on autoclose

[Xi Wang <xi.wang@gmail.com>]

Commit 8ffd3208 voids the previous patches f6778aab and 810c0719 for
limiting the maximum autoclose value.  If userspace passes in -1 on
32-bit platform, the overflow check didn't work and autoclose would be
set to 0xffffffff.

This patch defines a max_autoclose for limiting the value and exposes
it through sysctl.

Suggested-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
---
 include/net/sctp/structs.h |    4 ++++
 net/sctp/protocol.c        |    3 +++
 net/sctp/socket.c          |    4 ++--
 net/sctp/sysctl.c          |    7 +++++++
 4 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index e90e7a9..781f16d 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -241,6 +241,9 @@ extern struct sctp_globals {
 	 * bits is an indicator of when to send and window update SACK.
 	 */
 	int rwnd_update_shift;
+
+	/* Threshold for autoclose timeout. */
+	unsigned int max_autoclose;
 } sctp_globals;
 
 #define sctp_rto_initial		(sctp_globals.rto_initial)
@@ -281,6 +284,7 @@ extern struct sctp_globals {
 #define sctp_auth_enable		(sctp_globals.auth_enable)
 #define sctp_checksum_disable		(sctp_globals.checksum_disable)
 #define sctp_rwnd_upd_shift		(sctp_globals.rwnd_update_shift)
+#define sctp_max_autoclose		(sctp_globals.max_autoclose)
 
 /* SCTP Socket type: UDP or TCP style. */
 typedef enum {
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 61b9fca..4e07b18 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1285,6 +1285,9 @@ SCTP_STATIC __init int sctp_init(void)
 	sctp_max_instreams    		= SCTP_DEFAULT_INSTREAMS;
 	sctp_max_outstreams   		= SCTP_DEFAULT_OUTSTREAMS;
 
+	/* Initialize maximum autoclose timeout. */
+	sctp_max_autoclose		= INT_MAX;
+
 	/* Initialize handle used for association ids. */
 	idr_init(&sctp_assocs_id);
 
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 13bf5fc..f8c8e66 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -2200,8 +2200,8 @@ static int sctp_setsockopt_autoclose(struct sock *sk, char __user *optval,
 		return -EINVAL;
 	if (copy_from_user(&sp->autoclose, optval, optlen))
 		return -EFAULT;
-	/* make sure it won't exceed MAX_SCHEDULE_TIMEOUT */
-	sp->autoclose = min_t(long, sp->autoclose, MAX_SCHEDULE_TIMEOUT / HZ);
+	/* make sure it won't exceed sctp_max_autoclose / HZ */
+	sp->autoclose = min(sp->autoclose, sctp_max_autoclose / HZ);
 
 	return 0;
 }
diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index 6b39529..b74686e 100644
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -258,6 +258,13 @@ static ctl_table sctp_table[] = {
 		.extra1		= &one,
 		.extra2		= &rwnd_scale_max,
 	},
+	{
+		.procname	= "max_autoclose",
+		.data		= &sctp_max_autoclose,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_jiffies,
+	},
 
 	{ /* sentinel */ }
 };
-- 
1.7.5.4