From 2dd7d13d5c0516660b731167afe81e9be57b7b4e Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 9 Sep 2020 22:25:06 -0400 Subject: [PATCH] epoll: do not insert into poll queues until all sanity checks are done commit f8d4f44df056c5b504b0d49683fb7279218fd207 upstream. Mot-CRs-fixed: (CR) CVE-Fixed: CVE-2021-39634 Bug: 204450605 Change-Id: If2c466f2eecd8acdb152456d94a00210a4c0af74 Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman Signed-off-by: Gajjala Chakradhar Reviewed-on: https://gerrit.mot.com/2152183 SME-Granted: SME Approvals Granted SLTApproved: Slta Waiver Tested-by: Jira Key Reviewed-by: Xiangpo Zhao Submit-Approved: Jira Key --- fs/eventpoll.c | 37 ++++++++++++++++++------------------- 1 file changed, 18 insertions(+), 19 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index a10c6081e48f..b4ff1fee79cf 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1462,6 +1462,22 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, RCU_INIT_POINTER(epi->ws, NULL); } + /* Add the current item to the list of active epoll hook for this file */ + spin_lock(&tfile->f_lock); + list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links); + spin_unlock(&tfile->f_lock); + + /* + * Add the current item to the RB tree. All RB tree operations are + * protected by "mtx", and ep_insert() is called with "mtx" held. + */ + ep_rbtree_insert(ep, epi); + + /* now check if we've created too many backpaths */ + error = -EINVAL; + if (full_check && reverse_path_check()) + goto error_remove_epi; + /* Initialize the poll table using the queue callback */ epq.epi = epi; init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); @@ -1484,22 +1500,6 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, if (epi->nwait < 0) goto error_unregister; - /* Add the current item to the list of active epoll hook for this file */ - spin_lock(&tfile->f_lock); - list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links); - spin_unlock(&tfile->f_lock); - - /* - * Add the current item to the RB tree. All RB tree operations are - * protected by "mtx", and ep_insert() is called with "mtx" held. - */ - ep_rbtree_insert(ep, epi); - - /* now check if we've created too many backpaths */ - error = -EINVAL; - if (full_check && reverse_path_check()) - goto error_remove_epi; - /* We have to drop the new item inside our item list to keep track of it */ spin_lock_irqsave(&ep->lock, flags); @@ -1528,6 +1528,8 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event, return 0; +error_unregister: + ep_unregister_pollwait(ep, epi); error_remove_epi: spin_lock(&tfile->f_lock); list_del_rcu(&epi->fllink); @@ -1535,9 +1537,6 @@ error_remove_epi: rb_erase_cached(&epi->rbn, &ep->rbr); -error_unregister: - ep_unregister_pollwait(ep, epi); - /* * We need to do this because an event could have been arrived on some * allocated wait queue. Note that we don't care about the ep->ovflist -- 2.20.1