sctp: fix incorrect overflow check on autoclose

Commit 8ffd3208 voids the previous patches f6778aab and 810c0719 for
limiting the 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 (in seconds) for limiting the value
and exposes it through sysctl, with the following intentions.

1) Avoid overflowing autoclose * HZ.

2) Keep the default autoclose bound consistent across 32- and 64-bit
   platforms (INT_MAX / HZ in this patch).

3) Keep the autoclose value consistent between setsockopt() and
   getsockopt() calls.

Suggested-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 21 insertions, 3 deletions

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index e90e7a9935dd..a15432da27c3 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, in seconds. */
+        unsigned long 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/associola.c b/net/sctp/associola.c
index 152b5b3c3fff..acd2edbc073e 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -173,7 +173,7 @@ static struct sctp_association *sctp_association_init(struct sctp_association *a
         asoc->timeouts[SCTP_EVENT_TIMEOUT_HEARTBEAT] = 0;
         asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] = asoc->sackdelay;
         asoc->timeouts[SCTP_EVENT_TIMEOUT_AUTOCLOSE] =
-                (unsigned long)sp->autoclose * HZ;
+                min_t(unsigned long, sp->autoclose, sctp_max_autoclose) * HZ;
 
         /* Initializes the timers */
         for (i = SCTP_EVENT_TIMEOUT_NONE; i < SCTP_NUM_TIMEOUT_TYPES; ++i)
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 61b9fca5a173..6f6ad8686833 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 / HZ;
+
         /* Initialize handle used for association ids. */
         idr_init(&sctp_assocs_id);
 
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 13bf5fcdbff1..54a7cd2fdd7a 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -2200,8 +2200,6 @@ 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);
 
         return 0;
 }
diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index 6b3952961b85..60ffbd067ff7 100644
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -53,6 +53,10 @@ static int sack_timer_min = 1;
 static int sack_timer_max = 500;
 static int addr_scope_max = 3; /* check sctp_scope_policy_t in include/net/sctp/constants.h for max entries */
 static int rwnd_scale_max = 16;
+static unsigned long max_autoclose_min = 0;
+static unsigned long max_autoclose_max =
+        (MAX_SCHEDULE_TIMEOUT / HZ > UINT_MAX)
+        ? UINT_MAX : MAX_SCHEDULE_TIMEOUT / HZ;
 
 extern long sysctl_sctp_mem[3];
 extern int sysctl_sctp_rmem[3];
@@ -258,6 +262,15 @@ static ctl_table sctp_table[] = {
                 .extra1         = &one,
                 .extra2         = &rwnd_scale_max,
         },
+        {
+                .procname       = "max_autoclose",
+                .data           = &sctp_max_autoclose,
+                .maxlen         = sizeof(unsigned long),
+                .mode           = 0644,
+                .proc_handler   = &proc_doulongvec_minmax,
+                .extra1         = &max_autoclose_min,
+                .extra2         = &max_autoclose_max,
+        },
 
         { /* sentinel */ }
 };