Message ID | 1399541282-7472-1-git-send-email-luis.henriques@canonical.com |
---|---|
State | New |
Headers | show |
On Thu, May 08, 2014 at 10:28:02AM +0100, Luis Henriques wrote: > From: Vlastimil Babka <vbabka@suse.cz> > > A BUG_ON(!PageLocked) was triggered in mlock_vma_page() by Sasha Levin > fuzzing with trinity. The call site try_to_unmap_cluster() does not lock > the pages other than its check_page parameter (which is already locked). > > The BUG_ON in mlock_vma_page() is not documented and its purpose is > somewhat unclear, but apparently it serializes against page migration, > which could otherwise fail to transfer the PG_mlocked flag. This would > not be fatal, as the page would be eventually encountered again, but > NR_MLOCK accounting would become distorted nevertheless. This patch adds > a comment to the BUG_ON in mlock_vma_page() and munlock_vma_page() to that > effect. > > The call site try_to_unmap_cluster() is fixed so that for page != > check_page, trylock_page() is attempted (to avoid possible deadlocks as we > already have check_page locked) and mlock_vma_page() is performed only > upon success. If the page lock cannot be obtained, the page is left > without PG_mlocked, which is again not a problem in the whole unevictable > memory design. > > Signed-off-by: Vlastimil Babka <vbabka@suse.cz> > Signed-off-by: Bob Liu <bob.liu@oracle.com> > Reported-by: Sasha Levin <sasha.levin@oracle.com> > Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com> > Cc: Michel Lespinasse <walken@google.com> > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > Acked-by: Rik van Riel <riel@redhat.com> > Cc: David Rientjes <rientjes@google.com> > Cc: Mel Gorman <mgorman@suse.de> > Cc: Hugh Dickins <hughd@google.com> > Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> > Cc: <stable@vger.kernel.org> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> > (back ported from commit 57e68e9cd65b4b8eb4045a1e0d0746458502554c) > CVE-2014-3122 > BugLink: http://bugs.launchpad.net/bugs/1316268 > Signed-off-by: Luis Henriques <luis.henriques@canonical.com> > --- > mm/mlock.c | 2 ++ > mm/rmap.c | 14 ++++++++++++-- > 2 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/mm/mlock.c b/mm/mlock.c > index 32832726..019586f 100644 > --- a/mm/mlock.c > +++ b/mm/mlock.c > @@ -78,6 +78,7 @@ void __clear_page_mlock(struct page *page) > */ > void mlock_vma_page(struct page *page) > { > + /* Serialize with page migration */ > BUG_ON(!PageLocked(page)); > > if (!TestSetPageMlocked(page)) { > @@ -105,6 +106,7 @@ void mlock_vma_page(struct page *page) > */ > void munlock_vma_page(struct page *page) > { > + /* For try_to_munlock() and to serialize with page migration */ > BUG_ON(!PageLocked(page)); > > if (TestClearPageMlocked(page)) { > diff --git a/mm/rmap.c b/mm/rmap.c > index 2b03b31..e5b4407 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1441,9 +1441,19 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, > BUG_ON(!page || PageAnon(page)); > > if (locked_vma) { > - mlock_vma_page(page); /* no-op if already mlocked */ > - if (page == check_page) > + if (page == check_page) { > + /* we know we have check_page locked */ > + mlock_vma_page(page); > ret = SWAP_MLOCK; > + } else if (trylock_page(page)) { > + /* > + * If we can lock the page, perform mlock. > + * Otherwise leave the page alone, it will be > + * eventually encountered again later. > + */ > + mlock_vma_page(page); > + unlock_page(page); > + } > continue; /* don't unmap */ > } > > -- > 1.9.1 > > -- > kernel-team mailing list > kernel-team@lists.ubuntu.com > https://lists.ubuntu.com/mailman/listinfo/kernel-team Looks good to me, looks to be the upstream change. Indeed, I am unable to see how it is not a cherry-pick it is so similar :). So: Acked-by: Andy Whitcroft <apw@canonical.com> -apw
I see you say lts-quantal, acking for either/both depending if there are any more quantals. > Subject: Re: [CVE-2014-3122][Lucid][Precise/lts-backport-quantal] mm: > try_to_unmap_cluster() should lock_page() before mlocking -apw
diff --git a/mm/mlock.c b/mm/mlock.c index 32832726..019586f 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -78,6 +78,7 @@ void __clear_page_mlock(struct page *page) */ void mlock_vma_page(struct page *page) { + /* Serialize with page migration */ BUG_ON(!PageLocked(page)); if (!TestSetPageMlocked(page)) { @@ -105,6 +106,7 @@ void mlock_vma_page(struct page *page) */ void munlock_vma_page(struct page *page) { + /* For try_to_munlock() and to serialize with page migration */ BUG_ON(!PageLocked(page)); if (TestClearPageMlocked(page)) { diff --git a/mm/rmap.c b/mm/rmap.c index 2b03b31..e5b4407 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1441,9 +1441,19 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, BUG_ON(!page || PageAnon(page)); if (locked_vma) { - mlock_vma_page(page); /* no-op if already mlocked */ - if (page == check_page) + if (page == check_page) { + /* we know we have check_page locked */ + mlock_vma_page(page); ret = SWAP_MLOCK; + } else if (trylock_page(page)) { + /* + * If we can lock the page, perform mlock. + * Otherwise leave the page alone, it will be + * eventually encountered again later. + */ + mlock_vma_page(page); + unlock_page(page); + } continue; /* don't unmap */ }