epoll: convert max_user_watches to long

On a 16TB machine, max_user_watches has an integer overflow.  Convert it
to use a long and handle the associated fallout.

Signed-off-by: Robin Holt <holt@sgi.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 8 deletions

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 8cf07242067d..cc8a9b7d6064 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -217,7 +217,7 @@ struct ep_send_events_data {
  * Configuration options available inside /proc/sys/fs/epoll/
  */
 /* Maximum number of epoll watched descriptors, per user */
-static int max_user_watches __read_mostly;
+static long max_user_watches __read_mostly;
 
 /*
  * This mutex is used to serialize ep_free() and eventpoll_release_file().
@@ -240,16 +240,18 @@ static struct kmem_cache *pwq_cache __read_mostly;
 
 #include <linux/sysctl.h>
 
-static int zero;
+static long zero;
+static long long_max = LONG_MAX;
 
 ctl_table epoll_table[] = {
         {
                 .procname       = "max_user_watches",
                 .data           = &max_user_watches,
-                .maxlen         = sizeof(int),
+                .maxlen         = sizeof(max_user_watches),
                 .mode           = 0644,
-                .proc_handler   = proc_dointvec_minmax,
+                .proc_handler   = proc_doulongvec_minmax,
                 .extra1         = &zero,
+                .extra2         = &long_max,
         },
         { }
 };
@@ -561,7 +563,7 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi)
         /* At this point it is safe to free the eventpoll item */
         kmem_cache_free(epi_cache, epi);
 
-        atomic_dec(&ep->user->epoll_watches);
+        atomic_long_dec(&ep->user->epoll_watches);
 
         return 0;
 }
@@ -898,11 +900,12 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
 {
         int error, revents, pwake = 0;
         unsigned long flags;
+        long user_watches;
         struct epitem *epi;
         struct ep_pqueue epq;
 
-        if (unlikely(atomic_read(&ep->user->epoll_watches) >=
-                     max_user_watches))
+        user_watches = atomic_long_read(&ep->user->epoll_watches);
+        if (unlikely(user_watches >= max_user_watches))
                 return -ENOSPC;
         if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL)))
                 return -ENOMEM;
@@ -966,7 +969,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
 
         spin_unlock_irqrestore(&ep->lock, flags);
 
-        atomic_inc(&ep->user->epoll_watches);
+        atomic_long_inc(&ep->user->epoll_watches);
 
         /* We have to call this outside the lock */
         if (pwake)
@@ -1426,6 +1429,7 @@ static int __init eventpoll_init(void)
          */
         max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) /
                 EP_ITEM_COST;
+        BUG_ON(max_user_watches < 0);
 
         /* Initialize the structure used to perform safe poll wait head wake ups */
         ep_nested_calls_init(&poll_safewake_ncalls);