diff options
| author | Davide Libenzi <davidel@xmailserver.org> | 2009-01-29 14:25:26 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-29 18:04:45 -0800 |
| commit | 9df04e1f25effde823a600e755b51475d438f56b (patch) | |
| tree | 57a207adf5e4bfb010000724dc1482e421933be4 | |
| parent | 3095eb87bb36ae880608fe3fc46cfd59ced1f319 (diff) | |
epoll: drop max_user_instances and rely only on max_user_watches
Linus suggested to put limits where the money is, and max_user_watches
already does that w/out the need of max_user_instances. That has the
advantage to mitigate the potential DoS while allowing pretty generous
default behavior.
Allowing top 4% of low memory (per user) to be allocated in epoll watches,
we have:
LOMEM MAX_WATCHES (per user)
512MB ~178000
1GB ~356000
2GB ~712000
A box with 512MB of lomem, will meet some challenge in hitting 180K
watches, socket buffers math teaches us. No more max_user_instances
limits then.
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Bron Gondwana <brong@fastmail.fm>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/eventpoll.c | 22 | ||||
| -rw-r--r-- | include/linux/sched.h | 1 |
2 files changed, 4 insertions, 19 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index ba2f9ec7119..011b9b8c90c 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -234,8 +234,6 @@ struct ep_pqueue { /* * Configuration options available inside /proc/sys/fs/epoll/ */ -/* Maximum number of epoll devices, per user */ -static int max_user_instances __read_mostly; /* Maximum number of epoll watched descriptors, per user */ static int max_user_watches __read_mostly; @@ -261,14 +259,6 @@ static int zero; ctl_table epoll_table[] = { { - .procname = "max_user_instances", - .data = &max_user_instances, - .maxlen = sizeof(int), - .mode = 0644, - .proc_handler = &proc_dointvec_minmax, - .extra1 = &zero, - }, - { .procname = "max_user_watches", .data = &max_user_watches, .maxlen = sizeof(int), @@ -491,7 +481,6 @@ static void ep_free(struct eventpoll *ep) mutex_unlock(&epmutex); mutex_destroy(&ep->mtx); - atomic_dec(&ep->user->epoll_devs); free_uid(ep->user); kfree(ep); } @@ -581,10 +570,6 @@ static int ep_alloc(struct eventpoll **pep) struct eventpoll *ep; user = get_current_user(); - error = -EMFILE; - if (unlikely(atomic_read(&user->epoll_devs) >= - max_user_instances)) - goto free_uid; error = -ENOMEM; ep = kzalloc(sizeof(*ep), GFP_KERNEL); if (unlikely(!ep)) @@ -1141,7 +1126,6 @@ SYSCALL_DEFINE1(epoll_create1, int, flags) flags & O_CLOEXEC); if (fd < 0) ep_free(ep); - atomic_inc(&ep->user->epoll_devs); error_return: DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n", @@ -1366,8 +1350,10 @@ static int __init eventpoll_init(void) struct sysinfo si; si_meminfo(&si); - max_user_instances = 128; - max_user_watches = (((si.totalram - si.totalhigh) / 32) << PAGE_SHIFT) / + /* + * Allows top 4% of lomem to be allocated for epoll watches (per user). + */ + max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / EP_ITEM_COST; /* Initialize the structure used to perform safe poll wait head wake ups */ diff --git a/include/linux/sched.h b/include/linux/sched.h index 02e16d20730..5a7c7638873 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -630,7 +630,6 @@ struct user_struct { atomic_t inotify_devs; /* How many inotify devs does this user have opened? */ #endif #ifdef CONFIG_EPOLL - atomic_t epoll_devs; /* The number of epoll descriptors currently open */ atomic_t epoll_watches; /* The number of file descriptors currently watched */ #endif #ifdef CONFIG_POSIX_MQUEUE |