diff options
Diffstat (limited to 'fs/eventpoll.c')
| -rw-r--r-- | fs/eventpoll.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 0e65c7431dfc..eed8cecd94e3 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -459,11 +459,14 @@ static struct kmem_cache *pwq_cache __ro_after_init; * Wrapper anchor for file->f_ep when the watched file is not itself an * eventpoll; for the epoll-watches-epoll case, file->f_ep points at * &watched_ep->refs directly. The ->next field threads - * ctx->tfile_check_list during one EPOLL_CTL_ADD path check. + * ctx->tfile_check_list during one EPOLL_CTL_ADD path check. The ->file + * field holds a reference to the associated file while the head is on + * the list. */ struct epitems_head { struct hlist_head epitems; struct epitems_head *next; + struct file *file; }; static struct kmem_cache *ephead_cache __ro_after_init; @@ -480,6 +483,16 @@ static void list_file(struct file *file, struct ep_ctl_ctx *ctx) head = container_of(file->f_ep, struct epitems_head, epitems); if (!head->next) { + /* + * The caller owns a reference to @file or holds the ep->mtx for the + * epitem that led here. The latter blocks eventpoll_release_file() + * before the file allocation can be freed and reused. A dying leaf + * can be skipped since removing links cannot increase the reverse + * path count. + */ + if (!file_ref_get(&file->f_ref)) + return; + head->file = file; head->next = ctx->tfile_check_list; ctx->tfile_check_list = head; } @@ -489,15 +502,18 @@ static void unlist_file(struct epitems_head *head) { struct epitems_head *to_free = head; struct hlist_node *p = rcu_dereference(hlist_first_rcu(&head->epitems)); + struct file *file = head->file; if (p) { struct epitem *epi= container_of(p, struct epitem, fllink); spin_lock(&epi->ffd.file->f_lock); if (!hlist_empty(&head->epitems)) to_free = NULL; head->next = NULL; + head->file = NULL; spin_unlock(&epi->ffd.file->f_lock); } free_ephead(to_free); + fput(file); } #ifdef CONFIG_SYSCTL |