[34-longterm 229/247] epoll: convert max_user_watches to long

Paul Gortmaker
2011-06-23T17:45:00Z

From: Robin Holt <holt@sgi.com>

-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.
-------------------

commit 52bd19f7691b2ea6433aef0ef94c08c57efd7e79 upstream.

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>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
fs/eventpoll.c | 20 ++++++++++++--------
include/linux/sched.h | 2 +-
2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index a8dfe21..85c5a9f 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -227,7 +227,7 @@ 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().
@@ -253,16 +253,18 @@ 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,
},
{ }
};
@@ -574,7 +576,7 @@ 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;
}
@@ -910,11 +912,12 @@ 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;
@@ -978,7 +981,7 @@ 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)
@@ -1512,6 +1515,7 @@ 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 epoll file descriptor
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 03e34c5..c66e0af 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -672,7 +672,7 @@ struct user_struct {
atomic_t inotify_devs; /* How many inotify devs does this user have opened? */
#endif
#ifdef CONFIG_EPOLL
- atomic_t epoll_watches; /* The number of file descriptors currently watched */
+ atomic_long_t epoll_watches; /* The number of file descriptors currently watched */
#endif
#ifdef CONFIG_POSIX_MQUEUE
/* protected by mq_lock */
--
1.7.4.4