853388e615
back port upstream patch
ebe06187bf
the epi is removed from list by list_del_rcu(&epi->fllink);
under list_for_each_entry_rcu() without rcu_read_lock.
if the rcu grace-period thread free epi before next list_for_each loop,
the content of epi will be corrupted.
Change-Id: I75dbf8ada5ca4734761efe260ca6d6f85886b180
Closes-Bug: 1837430
Suggested-by: daniel.badea@windriver.com
Signed-off-by: Bin Yang <bin.yang@intel.com>
53 lines
1.8 KiB
Diff
53 lines
1.8 KiB
Diff
From ebe06187bf2aec10d537ce4595e416035367d703 Mon Sep 17 00:00:00 2001
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From: Konstantin Khlebnikov <koct9i@gmail.com>
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Date: Tue, 17 Jun 2014 06:58:05 +0400
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Subject: [PATCH] epoll: fix use-after-free in eventpoll_release_file
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This fixes use-after-free of epi->fllink.next inside list loop macro.
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This loop actually releases elements in the body. The list is
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rcu-protected but here we cannot hold rcu_read_lock because we need to
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lock mutex inside.
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The obvious solution is to use list_for_each_entry_safe(). RCU-ness
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isn't essential because nobody can change this list under us, it's final
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fput for this file.
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The bug was introduced by ae10b2b4eb01 ("epoll: optimize EPOLL_CTL_DEL
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using rcu")
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Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
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Reported-by: Cyrill Gorcunov <gorcunov@openvz.org>
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Cc: Stable <stable@vger.kernel.org> # 3.13+
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Cc: Sasha Levin <sasha.levin@oracle.com>
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Cc: Jason Baron <jbaron@akamai.com>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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fs/eventpoll.c | 4 ++--
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1 file changed, 2 insertions(+), 2 deletions(-)
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diff --git a/fs/eventpoll.c b/fs/eventpoll.c
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index b73e062..b10b48c 100644
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--- a/fs/eventpoll.c
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+++ b/fs/eventpoll.c
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@@ -910,7 +910,7 @@ static const struct file_operations eventpoll_fops = {
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void eventpoll_release_file(struct file *file)
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{
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struct eventpoll *ep;
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- struct epitem *epi;
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+ struct epitem *epi, *next;
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/*
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* We don't want to get "file->f_lock" because it is not
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@@ -926,7 +926,7 @@ void eventpoll_release_file(struct file *file)
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* Besides, ep_remove() acquires the lock, so we can't hold it here.
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*/
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mutex_lock(&epmutex);
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- list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) {
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+ list_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) {
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ep = epi->ep;
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mutex_lock_nested(&ep->mtx, 0);
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ep_remove(ep, epi);
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--
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2.7.4
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