From: Andrea Arcangeli <aarcange@redhat.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Jan Kara <jack@suse.cz>,
ross.zwisler@linux.intel.com, Michal Hocko <mhocko@suse.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
syzkaller <syzkaller@googlegroups.com>
Subject: Re: mm: fault in __do_fault
Date: Tue, 28 Feb 2017 16:42:01 +0100 [thread overview]
Message-ID: <20170228154201.GH5816@redhat.com> (raw)
In-Reply-To: <CACT4Y+YgntApw9WMLZwF_ncF4JQdA2FNHDpzM+8hb_FpCuuC_g@mail.gmail.com>
Hello Dmitry,
On Tue, Feb 28, 2017 at 03:04:53PM +0100, Dmitry Vyukov wrote:
> Hello,
>
> The following program triggers GPF in __do_fault:
> https://gist.githubusercontent.com/dvyukov/27345737fca18d92ef761e7fa08aec9b/raw/d99d02511d0bf9a8d6f6bd9c79d373a26924e974/gistfile1.txt
Can you verify this fix:
WARNING: multiple messages have this Message-ID (diff)
From: Andrea Arcangeli <aarcange@redhat.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Jan Kara <jack@suse.cz>,
ross.zwisler@linux.intel.com, Michal Hocko <mhocko@suse.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
syzkaller <syzkaller@googlegroups.com>
Subject: Re: mm: fault in __do_fault
Date: Tue, 28 Feb 2017 16:42:01 +0100 [thread overview]
Message-ID: <20170228154201.GH5816@redhat.com> (raw)
In-Reply-To: <CACT4Y+YgntApw9WMLZwF_ncF4JQdA2FNHDpzM+8hb_FpCuuC_g@mail.gmail.com>
Hello Dmitry,
On Tue, Feb 28, 2017 at 03:04:53PM +0100, Dmitry Vyukov wrote:
> Hello,
>
> The following program triggers GPF in __do_fault:
> https://gist.githubusercontent.com/dvyukov/27345737fca18d92ef761e7fa08aec9b/raw/d99d02511d0bf9a8d6f6bd9c79d373a26924e974/gistfile1.txt
Can you verify this fix:
>From a65381bc86d2963713b6a9c4a73cded7dd184282 Mon Sep 17 00:00:00 2001
From: Andrea Arcangeli <aarcange@redhat.com>
Date: Tue, 28 Feb 2017 16:36:59 +0100
Subject: [PATCH 1/1] userfaultfd: shmem: __do_fault requires VM_FAULT_NOPAGE
__do_fault assumes vmf->page has been initialized and is valid if
VM_FAULT_NOPAGE is not returned by vma->vm_ops->fault(vma, vmf).
handle_userfault() in turn should return VM_FAULT_NOPAGE if it doesn't
return VM_FAULT_SIGBUS or VM_FAULT_RETRY (the other two
possibilities).
This VM_FAULT_NOPAGE case is only invoked when signal are pending and
it didn't matter for anonymous memory before. It only started to
matter since shmem was introduced. hugetlbfs also takes a different
path and doesn't exercise __do_fault.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
---
fs/userfaultfd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index fb6d02b..de28f43 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -500,7 +500,7 @@ int handle_userfault(struct vm_fault *vmf, unsigned long reason)
* in such case.
*/
down_read(&mm->mmap_sem);
- ret = 0;
+ ret = VM_FAULT_NOPAGE;
}
}
next prev parent reply other threads:[~2017-02-28 15:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-28 14:04 mm: fault in __do_fault Dmitry Vyukov
2017-02-28 14:04 ` Dmitry Vyukov
2017-02-28 15:32 ` Kirill A. Shutemov
2017-02-28 15:32 ` Kirill A. Shutemov
2017-02-28 15:55 ` Andrea Arcangeli
2017-02-28 15:55 ` Andrea Arcangeli
2017-02-28 15:42 ` Andrea Arcangeli [this message]
2017-02-28 15:42 ` Andrea Arcangeli
2017-03-03 7:42 ` Dmitry Vyukov
2017-03-03 7:42 ` Dmitry Vyukov
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