From: "Lin, Ming" <minggr@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Hugh Dickins <hughd@google.com>
Cc: Simon Ser <contact@emersion.fr>, Peter Xu <peterx@redhat.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Matthew Wilcox <willy@infradead.org>,
Dan Williams <dan.j.williams@intel.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Will Deacon <will@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
David Herrmann <dh.herrmann@gmail.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Greg Kroah-Hartman <greg@kroah.com>,
"tytso@mit.edu" <tytso@mit.edu>
Subject: Re: Sealed memfd & no-fault mmap
Date: Sat, 29 May 2021 00:31:39 -0700 [thread overview]
Message-ID: <80c87e6b-6050-bf23-2185-ded408df4d0f@gmail.com> (raw)
In-Reply-To: <CAHk-=wjv3-eP7mSDJbuvaB+CbyyKc4g_nEzhQLcueOd0_YuiBg@mail.gmail.com>
On 5/28/2021 6:03 PM, Linus Torvalds wrote:
> On Fri, May 28, 2021 at 7:07 AM Lin, Ming <minggr@gmail.com> wrote:
>>
>> Does something like following draft patch on the right track?
>
> No, I don't think this can work:
>
>> + _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
>> + vma->vm_page_prot));
>
> You can't just blindly insert the zero pfn - for a shared write
> mapping, that would actually allow writes to the zeropage. That would
> be horrible.
I should check the vma is not writable.
diff --git a/mm/shmem.c b/mm/shmem.c
index 856d2d8d4cdf..fa23e38bc692 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1820,7 +1820,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
spinlock_t *ptl;
int ret;
- if (!IS_NOFAULT(inode))
+ if (!IS_NOFAULT(inode) || (vma->vm_flags & VM_WRITE))
return -EINVAL;
_dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr)
next prev parent reply other threads:[~2021-05-29 7:31 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-27 8:24 Sealed memfd & no-fault mmap Simon Ser
2021-04-27 16:51 ` Linus Torvalds
2021-04-29 15:48 ` Kirill A. Shutemov
2021-04-29 18:38 ` Peter Xu
2021-05-04 9:29 ` Simon Ser
2021-05-04 16:08 ` Linus Torvalds
2021-05-05 10:21 ` Simon Ser
2021-05-05 18:42 ` Linus Torvalds
2021-05-28 17:07 ` Lin, Ming
2021-05-29 1:03 ` Linus Torvalds
2021-05-29 7:31 ` Lin, Ming [this message]
2021-05-29 15:44 ` Linus Torvalds
2021-05-29 20:15 ` Hugh Dickins
2021-05-29 23:36 ` Ming Lin
2021-05-31 21:13 ` Ming Lin
2021-06-01 6:24 ` Linus Torvalds
2021-06-01 7:08 ` Ming Lin
2021-06-03 13:01 ` Simon Ser
2021-06-03 20:07 ` Ming Lin
2021-06-03 20:49 ` Simon Ser
2021-06-03 13:14 ` Simon Ser
2021-06-03 13:57 ` Matthew Wilcox
2021-06-03 14:48 ` Simon Ser
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