From: Christian Brauner <[email protected]> [ Upstream commit 0f7bdfd413000985de09fc39eb9efa1e091a3ce0 ]
Split __ep_remove() to delineate file removal from epoll item removal. Suggested-by: Linus Torvalds <[email protected]> Link: https://patch.msgid.link/[email protected] Signed-off-by: Christian Brauner (Amutable) <[email protected]> Stable-dep-of: a6dc643c6931 ("eventpoll: fix ep_remove struct eventpoll / struct file UAF") Signed-off-by: Quentin Schulz <[email protected]> Signed-off-by: Sasha Levin <[email protected]> (cherry picked from commit 85d684efb08991253d869b6010eed83cb0714468) Signed-off-by: Eva Kurchatova <[email protected]> https://virtuozzo.atlassian.net/browse/VSTOR-137490 Feature: fix epoll cve --- fs/eventpoll.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 254f0a19d0f2..6e04e1af97d7 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -826,6 +826,9 @@ static void ep_free(struct eventpoll *ep) kfree_rcu(ep, rcu); } +static void __ep_remove_file(struct eventpoll *ep, struct epitem *epi, struct file *file); +static bool __ep_remove_epi(struct eventpoll *ep, struct epitem *epi); + /* * Removes a "struct epitem" from the eventpoll RB tree and deallocates * all the associated resources. Must be called with "mtx" held. @@ -837,8 +840,6 @@ static void ep_free(struct eventpoll *ep) static bool __ep_remove(struct eventpoll *ep, struct epitem *epi, bool force) { struct file *file = epi->ffd.file; - struct epitems_head *to_free; - struct hlist_head *head; lockdep_assert_irqs_enabled(); @@ -854,8 +855,21 @@ static bool __ep_remove(struct eventpoll *ep, struct epitem *epi, bool force) return false; } - to_free = NULL; - head = file->f_ep; + __ep_remove_file(ep, epi, file); + return __ep_remove_epi(ep, epi); +} + +/* + * Called with &file->f_lock held, + * returns with it released + */ +static void __ep_remove_file(struct eventpoll *ep, struct epitem *epi, struct file *file) +{ + struct epitems_head *to_free = NULL; + struct hlist_head *head = file->f_ep; + + lockdep_assert_held(&ep->mtx); + if (hlist_is_singular_node(&epi->fllink, head)) { /* See eventpoll_release() for details. */ WRITE_ONCE(file->f_ep, NULL); @@ -869,6 +883,11 @@ static bool __ep_remove(struct eventpoll *ep, struct epitem *epi, bool force) hlist_del_rcu(&epi->fllink); spin_unlock(&file->f_lock); free_ephead(to_free); +} + +static bool __ep_remove_epi(struct eventpoll *ep, struct epitem *epi) +{ + lockdep_assert_held(&ep->mtx); rb_erase_cached(&epi->rbn, &ep->rbr); -- 2.55.0 _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
