From: Al Viro viro@zeniv.linux.org.uk
commit 18306c404abe18a0972587a6266830583c60c928 upstream.
removes the need to clear it, along with the races.
Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/eventpoll.c | 26 +++++++------------------- 1 file changed, 7 insertions(+), 19 deletions(-)
--- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -217,8 +217,7 @@ struct eventpoll { struct file *file;
/* used to optimize loop detection check */ - int visited; - struct list_head visited_list_link; + u64 gen; };
/* Wait structure used by the poll hooks */ @@ -262,6 +261,8 @@ static long max_user_watches __read_most */ static DEFINE_MUTEX(epmutex);
+static u64 loop_check_gen = 0; + /* Used to check for epoll file descriptor inclusion loops */ static struct nested_calls poll_loop_ncalls;
@@ -277,9 +278,6 @@ static struct kmem_cache *epi_cache __re /* 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. @@ -1696,13 +1694,12 @@ static int ep_loop_check_proc(void *priv struct epitem *epi;
mutex_lock_nested(&ep->mtx, call_nests + 1); - ep->visited = 1; - list_add(&ep->visited_list_link, &visited_list); + ep->gen = loop_check_gen; 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) + if (ep_tovisit->gen == loop_check_gen) continue; error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, ep_loop_check_proc, epi->ffd.file, @@ -1743,18 +1740,8 @@ static int ep_loop_check_proc(void *priv */ static int ep_loop_check(struct eventpoll *ep, struct file *file) { - int ret; - struct eventpoll *ep_cur, *ep_next; - - ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, + return ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, ep_loop_check_proc, file, ep, current); - /* clear visited list */ - list_for_each_entry_safe(ep_cur, ep_next, &visited_list, - visited_list_link) { - ep_cur->visited = 0; - list_del(&ep_cur->visited_list_link); - } - return ret; }
static void clear_tfile_check_list(void) @@ -1956,6 +1943,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, in error_tgt_fput: if (full_check) { clear_tfile_check_list(); + loop_check_gen++; mutex_unlock(&epmutex); }