From: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
To: Fuad Tabba <tabba@google.com>
Cc: Chao Peng <chao.p.peng@linux.intel.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-api@vger.kernel.org, linux-doc@vger.kernel.org,
qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
Hugh Dickins <hughd@google.com>, Jeff Layton <jlayton@kernel.org>,
"J . Bruce Fields" <bfields@fieldses.org>,
Andrew Morton <akpm@linux-foundation.org>,
Shuah Khan <shuah@kernel.org>, Mike Rapoport <rppt@kernel.org>,
Steven Price <steven.price@arm.com>,
"Maciej S . Szmigiero" <mail@maciej.szmigiero.name>,
Vlastimil Babka <vbabka@suse.cz>,
Vishal Annapurve <vannapurve@google.com>,
Yu Zhang <yu.c.zhang@linux.intel.com>,
luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com,
ak@linux.intel.com, david@redhat.com, aarcange@redhat.com,
ddutile@redhat.com, dhildenb@redhat.com,
Quentin Perret <qperret@google.com>,
Michael Roth <michael.roth@amd.com>,
mhocko@suse.com, Muchun Song <songmuchun@bytedance.com>,
wei.w.wang@intel.com
Subject: Re: [PATCH v8 1/8] mm/memfd: Introduce userspace inaccessible memfd
Date: Fri, 30 Sep 2022 19:23:01 +0300 [thread overview]
Message-ID: <20220930162301.i226o523teuikygq@box.shutemov.name> (raw)
In-Reply-To: <CA+EHjTyrexb_LX7Jm9-MGwm4DBvfjCrADH4oumFyAvs2_0oSYw@mail.gmail.com>
On Fri, Sep 30, 2022 at 05:14:00PM +0100, Fuad Tabba wrote:
> Hi,
>
> <...>
>
> > diff --git a/mm/memfd_inaccessible.c b/mm/memfd_inaccessible.c
> > new file mode 100644
> > index 000000000000..2d33cbdd9282
> > --- /dev/null
> > +++ b/mm/memfd_inaccessible.c
> > @@ -0,0 +1,219 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include "linux/sbitmap.h"
> > +#include <linux/memfd.h>
> > +#include <linux/pagemap.h>
> > +#include <linux/pseudo_fs.h>
> > +#include <linux/shmem_fs.h>
> > +#include <uapi/linux/falloc.h>
> > +#include <uapi/linux/magic.h>
> > +
> > +struct inaccessible_data {
> > + struct mutex lock;
> > + struct file *memfd;
> > + struct list_head notifiers;
> > +};
> > +
> > +static void inaccessible_notifier_invalidate(struct inaccessible_data *data,
> > + pgoff_t start, pgoff_t end)
> > +{
> > + struct inaccessible_notifier *notifier;
> > +
> > + mutex_lock(&data->lock);
> > + list_for_each_entry(notifier, &data->notifiers, list) {
> > + notifier->ops->invalidate(notifier, start, end);
> > + }
> > + mutex_unlock(&data->lock);
> > +}
> > +
> > +static int inaccessible_release(struct inode *inode, struct file *file)
> > +{
> > + struct inaccessible_data *data = inode->i_mapping->private_data;
> > +
> > + fput(data->memfd);
> > + kfree(data);
> > + return 0;
> > +}
> > +
> > +static long inaccessible_fallocate(struct file *file, int mode,
> > + loff_t offset, loff_t len)
> > +{
> > + struct inaccessible_data *data = file->f_mapping->private_data;
> > + struct file *memfd = data->memfd;
> > + int ret;
> > +
> > + if (mode & FALLOC_FL_PUNCH_HOLE) {
> > + if (!PAGE_ALIGNED(offset) || !PAGE_ALIGNED(len))
> > + return -EINVAL;
> > + }
> > +
> > + ret = memfd->f_op->fallocate(memfd, mode, offset, len);
>
> I think that shmem_file_operations.fallocate is only set if
> CONFIG_TMPFS is enabled (shmem.c). Should there be a check at
> initialization that fallocate is set, or maybe a config dependency, or
> can we count on it always being enabled?
It is already there:
config MEMFD_CREATE
def_bool TMPFS || HUGETLBFS
And we reject inaccessible memfd_create() for HUGETLBFS.
But if we go with a separate syscall, yes, we need the dependency.
> > + inaccessible_notifier_invalidate(data, offset, offset + len);
> > + return ret;
> > +}
> > +
>
> <...>
>
> > +void inaccessible_register_notifier(struct file *file,
> > + struct inaccessible_notifier *notifier)
> > +{
> > + struct inaccessible_data *data = file->f_mapping->private_data;
> > +
> > + mutex_lock(&data->lock);
> > + list_add(¬ifier->list, &data->notifiers);
> > + mutex_unlock(&data->lock);
> > +}
> > +EXPORT_SYMBOL_GPL(inaccessible_register_notifier);
>
> If the memfd wasn't marked as inaccessible, or more generally
> speaking, if the file isn't a memfd_inaccessible file, this ends up
> accessing an uninitialized pointer for the notifier list. Should there
> be a check for that here, and have this function return an error if
> that's not the case?
I think it is "don't do that" category. inaccessible_register_notifier()
caller has to know what file it operates on, no?
--
Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2022-09-30 16:24 UTC|newest]
Thread overview: 97+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-15 14:29 [PATCH v8 0/8] KVM: mm: fd-based approach for supporting KVM Chao Peng
2022-09-15 14:29 ` [PATCH v8 1/8] mm/memfd: Introduce userspace inaccessible memfd Chao Peng
2022-09-19 9:12 ` David Hildenbrand
2022-09-19 19:10 ` Sean Christopherson
2022-09-21 21:10 ` Andy Lutomirski
2022-09-22 13:23 ` Wang, Wei W
2022-09-23 15:20 ` Fuad Tabba
2022-09-23 15:19 ` Fuad Tabba
2022-09-26 14:23 ` Chao Peng
2022-09-26 15:51 ` Fuad Tabba
2022-09-27 22:47 ` Sean Christopherson
2022-09-30 16:19 ` Fuad Tabba
2022-10-13 13:34 ` Chao Peng
2022-10-17 10:31 ` Fuad Tabba
2022-10-17 14:58 ` Chao Peng
2022-10-17 19:05 ` Fuad Tabba
2022-10-19 13:30 ` Chao Peng
2022-10-18 0:33 ` Sean Christopherson
2022-10-19 15:04 ` Fuad Tabba
2022-09-23 0:58 ` Kirill A . Shutemov
2022-09-26 10:35 ` David Hildenbrand
2022-09-26 14:48 ` Kirill A. Shutemov
2022-09-26 14:53 ` David Hildenbrand
2022-09-27 23:23 ` Sean Christopherson
2022-09-28 13:36 ` Kirill A. Shutemov
2022-09-22 13:26 ` Wang, Wei W
2022-09-22 19:49 ` Sean Christopherson
2022-09-23 0:53 ` Kirill A . Shutemov
2022-09-23 15:20 ` Fuad Tabba
2022-09-30 16:14 ` Fuad Tabba
2022-09-30 16:23 ` Kirill A . Shutemov [this message]
2022-10-03 7:33 ` Fuad Tabba
2022-10-03 11:01 ` Kirill A. Shutemov
2022-10-04 15:39 ` Fuad Tabba
2022-10-06 8:50 ` Fuad Tabba
2022-10-06 13:04 ` Kirill A. Shutemov
2022-10-17 13:00 ` Vlastimil Babka
2022-10-17 16:19 ` Kirill A . Shutemov
2022-10-17 16:39 ` Gupta, Pankaj
2022-10-17 21:56 ` Kirill A . Shutemov
2022-10-18 13:42 ` Vishal Annapurve
2022-10-19 15:32 ` Kirill A . Shutemov
2022-10-20 10:50 ` Vishal Annapurve
2022-10-21 13:54 ` Chao Peng
2022-10-21 16:53 ` Sean Christopherson
2022-10-19 12:23 ` Vishal Annapurve
2022-10-21 13:47 ` Chao Peng
2022-10-21 16:18 ` Sean Christopherson
2022-10-24 14:59 ` Kirill A . Shutemov
2022-10-24 15:26 ` David Hildenbrand
2022-11-03 16:27 ` Vishal Annapurve
2022-09-15 14:29 ` [PATCH v8 2/8] KVM: Extend the memslot to support fd-based private memory Chao Peng
2022-09-16 9:14 ` Bagas Sanjaya
2022-09-16 9:53 ` Chao Peng
2022-09-26 10:26 ` Fuad Tabba
2022-09-26 14:04 ` Chao Peng
2022-09-29 22:45 ` Isaku Yamahata
2022-09-29 23:22 ` Sean Christopherson
2022-10-05 13:04 ` Jarkko Sakkinen
2022-10-05 22:05 ` Jarkko Sakkinen
2022-10-06 9:00 ` Fuad Tabba
2022-10-06 14:58 ` Jarkko Sakkinen
2022-10-06 15:07 ` Jarkko Sakkinen
2022-10-06 15:34 ` Sean Christopherson
2022-10-07 11:14 ` Jarkko Sakkinen
2022-10-07 14:58 ` Sean Christopherson
2022-10-07 21:54 ` Jarkko Sakkinen
2022-10-08 16:15 ` Jarkko Sakkinen
2022-10-08 17:35 ` Jarkko Sakkinen
2022-10-10 8:25 ` Chao Peng
2022-10-12 8:14 ` Jarkko Sakkinen
2022-09-15 14:29 ` [PATCH v8 3/8] KVM: Add KVM_EXIT_MEMORY_FAULT exit Chao Peng
2022-09-16 9:17 ` Bagas Sanjaya
2022-09-16 9:54 ` Chao Peng
2022-09-15 14:29 ` [PATCH v8 4/8] KVM: Use gfn instead of hva for mmu_notifier_retry Chao Peng
2022-09-15 14:29 ` [PATCH v8 5/8] KVM: Register/unregister the guest private memory regions Chao Peng
2022-09-26 10:36 ` Fuad Tabba
2022-09-26 14:07 ` Chao Peng
2022-10-11 9:48 ` Fuad Tabba
2022-10-12 2:35 ` Chao Peng
2022-10-17 10:15 ` Fuad Tabba
2022-10-17 22:17 ` Sean Christopherson
2022-10-19 13:23 ` Chao Peng
2022-10-19 15:02 ` Fuad Tabba
2022-10-19 16:09 ` Sean Christopherson
2022-10-19 18:32 ` Fuad Tabba
2022-09-15 14:29 ` [PATCH v8 6/8] KVM: Update lpage info when private/shared memory are mixed Chao Peng
2022-09-29 16:52 ` Isaku Yamahata
2022-09-30 8:59 ` Chao Peng
2022-09-15 14:29 ` [PATCH v8 7/8] KVM: Handle page fault for private memory Chao Peng
2022-10-14 18:57 ` Sean Christopherson
2022-10-17 14:48 ` Chao Peng
2022-09-15 14:29 ` [PATCH v8 8/8] KVM: Enable and expose KVM_MEM_PRIVATE Chao Peng
2022-10-04 14:55 ` Jarkko Sakkinen
2022-10-10 8:31 ` Chao Peng
2022-10-06 8:55 ` Fuad Tabba
2022-10-10 8:33 ` Chao Peng
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