From: Matthew Wilcox <willy@infradead.org>
To: Mark Hemment <markhemm@googlemail.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
longpeng2@huawei.com, arnd@arndb.de, dave.hansen@linux.intel.com,
david@redhat.com, rppt@kernel.org,
Suren Baghdasaryan <surenb@google.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC PATCH 0/6] Add support for shared PTEs across processes
Date: Mon, 24 Jan 2022 15:27:26 +0000 [thread overview]
Message-ID: <Ye7FXkkHjOtHNxLp@casper.infradead.org> (raw)
In-Reply-To: <CANe_+Uiw1mSnFFBW3n5qBJ+V9EDaqY1PAEXFTXF9mkwM73x0-Q@mail.gmail.com>
On Mon, Jan 24, 2022 at 03:15:36PM +0000, Mark Hemment wrote:
> From the code sample in your initial email (simplified), where a
> process creates a msharefs file with the anonymous mmap()ed region to
> be shared;
> addr = mmap(RDWR, ANON);
> mshare("testregion", addr, len, CREAT|RDWR|EXCL, 0600);
>
> Now, consider the case where the mmap() is named (that is, against a
> file). I believe this is the usecase for Oracle's SGA.
> My (simplified) code for msharing a named file ("SGA") using your
> proposed API (does not matter if the mapping is PRIVATE or SHARED);
> fd = open("SGA", RDWR);
> addr = mmap(RDWR, ..., fd);
> mshare("SGA-region", addr, len, CREAT|RDWR|EXCL, 0600);
Don't think of an mshared region as containing only one file.
It might easily contain dozens. Or none at the start. They're
dynamic; the mshare fd represents a chunk of address space, not
whatever is currently mapped there.
> If the permissions (usr/grp+perms+ACL) between the "SGA" file and the
> "SGA-region" msharefs are different, then it is very likely a serious
> security issue.
Only in the same sense that an application might open() a file that it
has permission to access and then open a pipe/socket to a process that
does not have permission and send the data to it.
next prev parent reply other threads:[~2022-01-24 15:27 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-18 21:19 [RFC PATCH 0/6] Add support for shared PTEs across processes Khalid Aziz
2022-01-18 21:19 ` [RFC PATCH 1/6] mm: Add new system calls mshare, mshare_unlink Khalid Aziz
2022-01-18 21:19 ` [RFC PATCH 2/6] mm: Add msharefs filesystem Khalid Aziz
2022-01-18 21:19 ` [RFC PATCH 3/6] mm: Add read for msharefs Khalid Aziz
2022-01-18 21:19 ` [RFC PATCH 4/6] mm: implement mshare_unlink syscall Khalid Aziz
2022-01-18 21:19 ` [RFC PATCH 5/6] mm: Add locking to msharefs syscalls Khalid Aziz
2022-01-18 21:19 ` [RFC PATCH 6/6] mm: Add basic page table sharing using mshare Khalid Aziz
2022-01-18 21:41 ` [RFC PATCH 0/6] Add support for shared PTEs across processes Dave Hansen
2022-01-18 21:46 ` Matthew Wilcox
2022-01-18 22:47 ` Khalid Aziz
2022-01-18 22:06 ` Dave Hansen
2022-01-18 22:52 ` Khalid Aziz
2022-01-19 11:38 ` Mark Hemment
2022-01-19 17:02 ` Khalid Aziz
2022-01-20 12:49 ` Mark Hemment
2022-01-20 19:15 ` Khalid Aziz
2022-01-24 15:15 ` Mark Hemment
2022-01-24 15:27 ` Matthew Wilcox [this message]
2022-01-24 22:20 ` Khalid Aziz
2022-01-21 1:08 ` Barry Song
2022-01-21 2:13 ` Matthew Wilcox
2022-01-21 7:35 ` Barry Song
2022-01-21 14:47 ` Matthew Wilcox
2022-01-21 16:41 ` Khalid Aziz
2022-01-22 1:39 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2022-01-22 1:41 ` Matthew Wilcox
2022-01-22 10:18 ` Thomas Schoebel-Theuer
2022-01-22 16:09 ` Matthew Wilcox
2022-01-22 11:31 ` Mike Rapoport
2022-01-22 18:29 ` Andy Lutomirski
2022-01-24 18:48 ` Khalid Aziz
2022-01-24 19:45 ` Andy Lutomirski
2022-01-24 22:30 ` Khalid Aziz
2022-01-24 23:16 ` Andy Lutomirski
2022-01-24 23:44 ` Khalid Aziz
2022-01-25 11:42 ` Kirill A. Shutemov
2022-01-25 12:09 ` William Kucharski
2022-01-25 13:18 ` David Hildenbrand
2022-01-25 14:01 ` Kirill A. Shutemov
2022-01-25 13:23 ` Matthew Wilcox
2022-01-25 13:59 ` Kirill A. Shutemov
2022-01-25 14:09 ` Matthew Wilcox
2022-01-25 18:57 ` Kirill A. Shutemov
2022-01-25 18:59 ` Matthew Wilcox
2022-01-26 4:04 ` Matthew Wilcox
2022-01-26 10:16 ` David Hildenbrand
2022-01-26 13:38 ` Matthew Wilcox
2022-01-26 13:55 ` David Hildenbrand
2022-01-26 14:12 ` Matthew Wilcox
2022-01-26 14:30 ` David Hildenbrand
2022-01-26 14:12 ` Mike Rapoport
2022-01-26 13:42 ` Kirill A. Shutemov
2022-01-26 14:18 ` Mike Rapoport
2022-01-26 17:33 ` Khalid Aziz
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