From: Chao Peng <chao.p.peng@linux.intel.com>
To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
qemu-devel@nongnu.org
Cc: 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>,
Yu Zhang <yu.c.zhang@linux.intel.com>,
Chao Peng <chao.p.peng@linux.intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com,
ak@linux.intel.com, david@redhat.com
Subject: [PATCH v4 01/12] mm/shmem: Introduce F_SEAL_INACCESSIBLE
Date: Tue, 18 Jan 2022 21:21:10 +0800 [thread overview]
Message-ID: <20220118132121.31388-2-chao.p.peng@linux.intel.com> (raw)
In-Reply-To: <20220118132121.31388-1-chao.p.peng@linux.intel.com>
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Introduce a new seal F_SEAL_INACCESSIBLE indicating the content of
the file is inaccessible from userspace through ordinary MMU access
(e.g., read/write/mmap). However, the file content can be accessed
via a different mechanism (e.g. KVM MMU) indirectly.
It provides semantics required for KVM guest private memory support
that a file descriptor with this seal set is going to be used as the
source of guest memory in confidential computing environments such
as Intel TDX/AMD SEV but may not be accessible from host userspace.
At this time only shmem implements this seal.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
include/uapi/linux/fcntl.h | 1 +
mm/shmem.c | 40 ++++++++++++++++++++++++++++++++++++--
2 files changed, 39 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
index 2f86b2ad6d7e..09ef34754dfa 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h
@@ -43,6 +43,7 @@
#define F_SEAL_GROW 0x0004 /* prevent file from growing */
#define F_SEAL_WRITE 0x0008 /* prevent writes */
#define F_SEAL_FUTURE_WRITE 0x0010 /* prevent future writes while mapped */
+#define F_SEAL_INACCESSIBLE 0x0020 /* prevent ordinary MMU access (e.g. read/write/mmap) to file content */
/* (1U << 31) is reserved for signed error codes */
/*
diff --git a/mm/shmem.c b/mm/shmem.c
index 18f93c2d68f1..72185630e7c4 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1098,6 +1098,13 @@ static int shmem_setattr(struct user_namespace *mnt_userns,
(newsize > oldsize && (info->seals & F_SEAL_GROW)))
return -EPERM;
+ if (info->seals & F_SEAL_INACCESSIBLE) {
+ if(i_size_read(inode))
+ return -EPERM;
+ if (newsize & ~PAGE_MASK)
+ return -EINVAL;
+ }
+
if (newsize != oldsize) {
error = shmem_reacct_size(SHMEM_I(inode)->flags,
oldsize, newsize);
@@ -1364,6 +1371,8 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
goto redirty;
if (!total_swap_pages)
goto redirty;
+ if (info->seals & F_SEAL_INACCESSIBLE)
+ goto redirty;
/*
* Our capabilities prevent regular writeback or sync from ever calling
@@ -2262,6 +2271,9 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
if (ret)
return ret;
+ if (info->seals & F_SEAL_INACCESSIBLE)
+ return -EPERM;
+
/* arm64 - allow memory tagging on RAM-based files */
vma->vm_flags |= VM_MTE_ALLOWED;
@@ -2459,12 +2471,15 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
pgoff_t index = pos >> PAGE_SHIFT;
/* i_rwsem is held by caller */
- if (unlikely(info->seals & (F_SEAL_GROW |
- F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))) {
+ if (unlikely(info->seals & (F_SEAL_GROW | F_SEAL_WRITE |
+ F_SEAL_FUTURE_WRITE |
+ F_SEAL_INACCESSIBLE))) {
if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))
return -EPERM;
if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
return -EPERM;
+ if (info->seals & F_SEAL_INACCESSIBLE)
+ return -EPERM;
}
return shmem_getpage(inode, index, pagep, SGP_WRITE);
@@ -2538,6 +2553,21 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
end_index = i_size >> PAGE_SHIFT;
if (index > end_index)
break;
+
+ /*
+ * inode_lock protects setting up seals as well as write to
+ * i_size. Setting F_SEAL_INACCESSIBLE only allowed with
+ * i_size == 0.
+ *
+ * Check F_SEAL_INACCESSIBLE after i_size. It effectively
+ * serialize read vs. setting F_SEAL_INACCESSIBLE without
+ * taking inode_lock in read path.
+ */
+ if (SHMEM_I(inode)->seals & F_SEAL_INACCESSIBLE) {
+ error = -EPERM;
+ break;
+ }
+
if (index == end_index) {
nr = i_size & ~PAGE_MASK;
if (nr <= offset)
@@ -2663,6 +2693,12 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
goto out;
}
+ if ((info->seals & F_SEAL_INACCESSIBLE) &&
+ (offset & ~PAGE_MASK || len & ~PAGE_MASK)) {
+ error = -EINVAL;
+ goto out;
+ }
+
shmem_falloc.waitq = &shmem_falloc_waitq;
shmem_falloc.start = (u64)unmap_start >> PAGE_SHIFT;
shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
--
2.17.1
next prev parent reply other threads:[~2022-01-18 13:22 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-18 13:21 [PATCH v4 00/12] KVM: mm: fd-based approach for supporting KVM guest private memory Chao Peng
2022-01-18 13:21 ` Chao Peng [this message]
2022-02-07 12:24 ` [PATCH v4 01/12] mm/shmem: Introduce F_SEAL_INACCESSIBLE Vlastimil Babka
2022-02-17 12:56 ` Chao Peng
2022-02-11 23:33 ` Andy Lutomirski
2022-02-17 13:06 ` Chao Peng
2022-02-17 19:09 ` Andy Lutomirski
2022-02-23 11:49 ` Chao Peng
2022-02-23 12:05 ` Steven Price
2022-03-04 19:24 ` Andy Lutomirski
2022-03-07 13:26 ` Chao Peng
2022-03-08 12:17 ` Paolo Bonzini
2022-01-18 13:21 ` [PATCH v4 02/12] mm/memfd: Introduce MFD_INACCESSIBLE flag Chao Peng
2022-01-21 15:50 ` Steven Price
2022-01-24 13:29 ` Chao Peng
2022-02-07 18:51 ` Vlastimil Babka
2022-02-08 8:49 ` David Hildenbrand
2022-02-08 18:22 ` Mike Rapoport
2022-01-18 13:21 ` [PATCH v4 03/12] mm: Introduce memfile_notifier Chao Peng
2022-03-07 15:42 ` Vlastimil Babka
2022-03-08 1:45 ` Chao Peng
2022-01-18 13:21 ` [PATCH v4 04/12] mm/shmem: Support memfile_notifier Chao Peng
2022-02-08 18:29 ` Mike Rapoport
2022-02-17 13:10 ` Chao Peng
2022-02-11 23:40 ` Andy Lutomirski
2022-02-17 13:23 ` Chao Peng
2022-01-18 13:21 ` [PATCH v4 05/12] KVM: Extend the memslot to support fd-based private memory Chao Peng
2022-01-18 13:21 ` [PATCH v4 06/12] KVM: Use kvm_userspace_memory_region_ext Chao Peng
2022-01-18 13:21 ` [PATCH v4 07/12] KVM: Add KVM_EXIT_MEMORY_ERROR exit Chao Peng
2022-01-18 13:21 ` [PATCH v4 08/12] KVM: Use memfile_pfn_ops to obtain pfn for private pages Chao Peng
2022-01-18 13:21 ` [PATCH v4 09/12] KVM: Handle page fault for private memory Chao Peng
2022-01-18 13:21 ` [PATCH v4 10/12] KVM: Register private memslot to memory backing store Chao Peng
2022-01-18 13:21 ` [PATCH v4 11/12] KVM: Zap existing KVM mappings when pages changed in the private fd Chao Peng
2022-01-18 13:21 ` [PATCH v4 12/12] KVM: Expose KVM_MEM_PRIVATE Chao Peng
2022-01-25 20:20 ` Maciej S. Szmigiero
2022-02-17 13:45 ` Chao Peng
2022-02-22 1:16 ` Maciej S. Szmigiero
2022-02-23 12:00 ` Chao Peng
2022-02-23 18:32 ` Maciej S. Szmigiero
2022-02-24 8:07 ` Chao Peng
2022-01-28 16:47 ` [PATCH v4 00/12] KVM: mm: fd-based approach for supporting KVM guest private memory Steven Price
2022-02-02 2:28 ` Nakajima, Jun
2022-02-02 9:23 ` Steven Price
2022-02-02 20:47 ` Nakajima, Jun
2022-02-08 18:33 ` Mike Rapoport
2022-02-17 13:47 ` Chao Peng
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