| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Thu, 15 Jan 2015 21:02:40 +0000 (GMT)
From: Jason Baron <jbaron@...mai.com>
To: akpm@...ux-foundation.org, famz@...hat.com
Cc: normalperson@...t.net, nzimmer@....com, viro@...iv.linux.org.uk,
davidel@...ilserver.org, rostedt@...dmis.org,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [RFC PATCH 4/5] epoll: Allow topology checks to be parallelized
The ep_loop_check() (which checks for loops) and the reverse_path_check()
(which prevents excessively deep wakeup paths), functions currently make
use of a number of global variables, since they are always called under the
global 'epmutex'. In preparation, for removing the 'epmutex', we make use
of per-instance data structures, such that these topology checks can safely
be made in parallel. In addition, we make use of the ep_call_nested_nolock(),
which avoids the nested_calls->lock. This is safe here, since we are already
holding the 'epmutex' across all of these calls.
Signed-off-by: Jason Baron <jbaron@...mai.com>
---
fs/eventpoll.c | 148 +++++++++++++++++++++++++++++----------------------------
1 file changed, 76 insertions(+), 72 deletions(-)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index d0a021a..8fb23f4 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -251,6 +251,14 @@ struct ep_send_events_data {
struct epoll_event __user *events;
};
+struct loop_check_arg {
+ struct file *file;
+ struct nested_calls *loop_check_ncalls;
+ struct list_head *visited_list;
+ struct list_head *loop_check_list;
+ u16 *path_count_arr;
+};
+
/*
* Configuration options available inside /proc/sys/fs/epoll/
*/
@@ -262,24 +270,12 @@ static long max_user_watches __read_mostly;
*/
static DEFINE_MUTEX(epmutex);
-/* Used to check for epoll file descriptor inclusion loops */
-static struct nested_calls poll_loop_ncalls;
-
/* Slab cache used to allocate "struct epitem" */
static struct kmem_cache *epi_cache __read_mostly;
/* Slab cache used to allocate "struct eppoll_entry" */
static struct kmem_cache *pwq_cache __read_mostly;
-/* Visited nodes during ep_loop_check(), so we can unset them when we finish */
-static LIST_HEAD(visited_list);
-
-/*
- * List of files with newly added links, where we may need to limit the number
- * of emanating paths. Protected by the epmutex.
- */
-static LIST_HEAD(tfile_check_list);
-
#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
@@ -353,13 +349,6 @@ static inline int ep_op_has_event(int op)
return op != EPOLL_CTL_DEL;
}
-/* Initialize the poll safe wake up structure */
-static void ep_nested_calls_init(struct nested_calls *ncalls)
-{
- INIT_LIST_HEAD(&ncalls->tasks_call_list);
- spin_lock_init(&ncalls->lock);
-}
-
/**
* ep_events_available - Checks if ready events might be available.
*
@@ -477,6 +466,13 @@ out_unlock:
static struct nested_calls poll_safewake_ncalls;
+/* Initialize the poll safe wake up structure */
+static void ep_nested_calls_init(struct nested_calls *ncalls)
+{
+ INIT_LIST_HEAD(&ncalls->tasks_call_list);
+ spin_lock_init(&ncalls->lock);
+}
+
static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests)
{
unsigned long flags;
@@ -1111,9 +1107,6 @@ static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
rb_insert_color(&epi->rbn, &ep->rbr);
}
-
-
-#define PATH_ARR_SIZE 5
/*
* These are the number paths of length 1 to 5, that we are allowing to emanate
* from a single file of interest. For example, we allow 1000 paths of length
@@ -1125,32 +1118,26 @@ static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
* path limits are enforced during an EPOLL_CTL_ADD operation, since a modify
* and delete can't add additional paths. Protected by the epmutex.
*/
-static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 };
-static int path_count[PATH_ARR_SIZE];
+static const u16 path_limits[EP_MAX_NESTS] = { 500, 100, 50, 10 };
-static int path_count_inc(int nests)
+static int path_count_inc(int nests, u16 *path_count_arr)
{
+ BUG_ON(nests < 0 || nests >= EP_MAX_NESTS);
+
/* Allow an arbitrary number of depth 1 paths */
if (nests == 0)
return 0;
- if (++path_count[nests] > path_limits[nests])
+ if (++path_count_arr[nests - 1] > path_limits[nests - 1])
return -1;
return 0;
}
-static void path_count_init(void)
-{
- int i;
-
- for (i = 0; i < PATH_ARR_SIZE; i++)
- path_count[i] = 0;
-}
-
static int reverse_path_check_proc(void *priv, void *cookie, int call_nests)
{
int error = 0;
- struct file *file = priv;
+ struct loop_check_arg *args = priv;
+ struct file *file = args->file;
struct file *child_file;
struct epitem *epi;
@@ -1160,15 +1147,18 @@ static int reverse_path_check_proc(void *priv, void *cookie, int call_nests)
child_file = epi->ep->file;
if (is_file_epoll(child_file)) {
if (list_empty(&child_file->f_ep_links)) {
- if (path_count_inc(call_nests)) {
+ if (path_count_inc(call_nests,
+ args->path_count_arr)) {
error = -1;
break;
}
} else {
- error = ep_call_nested(&poll_loop_ncalls,
+ args->file = child_file;
+ error = ep_call_nested_nolock(
+ args->loop_check_ncalls,
EP_MAX_NESTS,
reverse_path_check_proc,
- child_file, child_file,
+ args, child_file,
current);
}
if (error != 0)
@@ -1192,17 +1182,24 @@ static int reverse_path_check_proc(void *priv, void *cookie, int call_nests)
* Returns: Returns zero if the proposed links don't create too many paths,
* -1 otherwise.
*/
-static int reverse_path_check(void)
+static int reverse_path_check(struct list_head *loop_check_list)
{
int error = 0;
struct file *current_file;
-
+ struct nested_calls reverse_loop_ncalls;
+ struct loop_check_arg args;
+ u16 path_count[EP_MAX_NESTS];
+
+ args.loop_check_ncalls = &reverse_loop_ncalls;
+ INIT_LIST_HEAD(&reverse_loop_ncalls.tasks_call_list);
+ memset(path_count, 0, sizeof(path_count));
+ args.path_count_arr = path_count;
/* let's call this for all tfiles */
- list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) {
- path_count_init();
- error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
- reverse_path_check_proc, current_file,
- current_file, current);
+ list_for_each_entry(current_file, loop_check_list, f_tfile_llink) {
+ args.file = current_file;
+ error = ep_call_nested_nolock(&reverse_loop_ncalls,
+ EP_MAX_NESTS, reverse_path_check_proc,
+ &args, current_file, current);
if (error)
break;
}
@@ -1250,7 +1247,8 @@ static noinline void ep_destroy_wakeup_source(struct epitem *epi)
* Must be called with "mtx" held.
*/
static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
- struct file *tfile, int fd, int full_check)
+ struct file *tfile, int fd, int full_check,
+ struct list_head *loop_check_list)
{
int error, revents, pwake = 0;
unsigned long flags;
@@ -1316,7 +1314,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
/* now check if we've created too many backpaths */
error = -EINVAL;
- if (full_check && reverse_path_check())
+ if (full_check && reverse_path_check(loop_check_list))
goto error_remove_epi;
/* We have to drop the new item inside our item list to keep track of it */
@@ -1667,7 +1665,8 @@ check_events:
static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
{
int error = 0;
- struct file *file = priv;
+ struct loop_check_arg *args = priv;
+ struct file *file = args->file;
struct eventpoll *ep = file->private_data;
struct eventpoll *ep_tovisit;
struct rb_node *rbp;
@@ -1675,15 +1674,16 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
mutex_lock_nested(&ep->mtx, call_nests + 1);
ep->visited = 1;
- list_add(&ep->visited_list_link, &visited_list);
+ list_add(&ep->visited_list_link, args->visited_list);
for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
epi = rb_entry(rbp, struct epitem, rbn);
if (unlikely(is_file_epoll(epi->ffd.file))) {
ep_tovisit = epi->ffd.file->private_data;
if (ep_tovisit->visited)
continue;
- error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
- ep_loop_check_proc, epi->ffd.file,
+ args->file = epi->ffd.file;
+ error = ep_call_nested_nolock(args->loop_check_ncalls,
+ EP_MAX_NESTS, ep_loop_check_proc, args,
ep_tovisit, current);
if (error != 0)
break;
@@ -1698,7 +1698,7 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
*/
if (list_empty(&epi->ffd.file->f_tfile_llink))
list_add(&epi->ffd.file->f_tfile_llink,
- &tfile_check_list);
+ args->loop_check_list);
}
}
mutex_unlock(&ep->mtx);
@@ -1717,13 +1717,22 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
* Returns: Returns zero if adding the epoll @file inside current epoll
* structure @ep does not violate the constraints, or -1 otherwise.
*/
-static int ep_loop_check(struct eventpoll *ep, struct file *file)
+static int ep_loop_check(struct eventpoll *ep, struct file *file,
+ struct list_head *loop_check_list)
{
int ret;
struct eventpoll *ep_cur, *ep_next;
-
- ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
- ep_loop_check_proc, file, ep, current);
+ struct nested_calls loop_check_ncalls;
+ struct loop_check_arg args;
+ LIST_HEAD(visited_list);
+
+ args.file = file;
+ args.visited_list = &visited_list;
+ args.loop_check_list = loop_check_list;
+ args.loop_check_ncalls = &loop_check_ncalls;
+ INIT_LIST_HEAD(&loop_check_ncalls.tasks_call_list);
+ ret = ep_call_nested_nolock(&loop_check_ncalls, EP_MAX_NESTS,
+ ep_loop_check_proc, &args, ep, current);
/* clear visited list */
list_for_each_entry_safe(ep_cur, ep_next, &visited_list,
visited_list_link) {
@@ -1733,17 +1742,15 @@ static int ep_loop_check(struct eventpoll *ep, struct file *file)
return ret;
}
-static void clear_tfile_check_list(void)
+static void clear_tfile_list(struct list_head *loop_check_list)
{
struct file *file;
- /* first clear the tfile_check_list */
- while (!list_empty(&tfile_check_list)) {
- file = list_first_entry(&tfile_check_list, struct file,
+ while (!list_empty(loop_check_list)) {
+ file = list_first_entry(loop_check_list, struct file,
f_tfile_llink);
list_del_init(&file->f_tfile_llink);
}
- INIT_LIST_HEAD(&tfile_check_list);
}
/*
@@ -1815,6 +1822,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
struct epitem *epi;
struct epoll_event epds;
struct eventpoll *tep = NULL;
+ LIST_HEAD(loop_check_list);
error = -EFAULT;
if (ep_op_has_event(op) &&
@@ -1879,13 +1887,14 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
mutex_lock(&epmutex);
if (is_file_epoll(tf.file)) {
error = -ELOOP;
- if (ep_loop_check(ep, tf.file) != 0) {
- clear_tfile_check_list();
+ if (ep_loop_check(ep, tf.file,
+ &loop_check_list) != 0) {
+ clear_tfile_list(&loop_check_list);
goto error_tgt_fput;
}
} else
list_add(&tf.file->f_tfile_llink,
- &tfile_check_list);
+ &loop_check_list);
mutex_lock_nested(&ep->mtx, 0);
if (is_file_epoll(tf.file)) {
tep = tf.file->private_data;
@@ -1906,11 +1915,12 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
case EPOLL_CTL_ADD:
if (!epi) {
epds.events |= POLLERR | POLLHUP;
- error = ep_insert(ep, &epds, tf.file, fd, full_check);
+ error = ep_insert(ep, &epds, tf.file, fd, full_check,
+ &loop_check_list);
} else
error = -EEXIST;
if (full_check)
- clear_tfile_check_list();
+ clear_tfile_list(&loop_check_list);
break;
case EPOLL_CTL_DEL:
if (epi)
@@ -2090,12 +2100,6 @@ static int __init eventpoll_init(void)
EP_ITEM_COST;
BUG_ON(max_user_watches < 0);
- /*
- * Initialize the structure used to perform epoll file descriptor
- * inclusion loops checks.
- */
- ep_nested_calls_init(&poll_loop_ncalls);
-
#ifdef CONFIG_DEBUG_LOCK_ALLOC
/* Initialize the structure used to perform safe poll wait head wake ups */
ep_nested_calls_init(&poll_safewake_ncalls);
--
1.8.2.rc2
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists