dri-devel Archive on lore.kernel.org
 help / color / Atom feed
From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: DRI Development <dri-devel@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>
Cc: linux-samsung-soc@vger.kernel.org, "Jan Kara" <jack@suse.cz>,
	"Kees Cook" <keescook@chromium.org>,
	kvm@vger.kernel.org, "Jason Gunthorpe" <jgg@ziepe.ca>,
	"Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"Christoph Hellwig" <hch@infradead.org>,
	linux-mm@kvack.org, "Jérôme Glisse" <jglisse@redhat.com>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-media@vger.kernel.org
Subject: [PATCH v7 17/17] mm: add mmu_notifier argument to follow_pfn
Date: Fri, 27 Nov 2020 17:41:31 +0100
Message-ID: <20201127164131.2244124-18-daniel.vetter@ffwll.ch> (raw)
In-Reply-To: <20201127164131.2244124-1-daniel.vetter@ffwll.ch>

The only safe way for non core/arch code to use follow_pfn() is
together with an mmu_notifier subscription. follow_pfn() is already
marked as _GPL and the kerneldoc explains this restriction.

This patch here enforces all this by adding a mmu_notifier argument
and verifying that it is registered for the correct mm_struct.

Motivated by discussions with Christoph Hellwig and Jason Gunthorpe.

Since requiring an mmu_notifier makes it very clear that follow_pfn()
cannot be used on !CONFIG_MMU hardware, remove it from there. The sole
user kvm not existing on such hardware also supports that.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-media@vger.kernel.org
Cc: kvm@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
--
v7: Comments from Jason:
- ditch follow_pfn from nommu.c
- simplify mmu_notifer->mm check
---
 include/linux/mm.h  |  3 ++-
 mm/memory.c         | 38 ++++++++++++++++++++++++--------------
 mm/nommu.c          | 27 +++++----------------------
 virt/kvm/kvm_main.c |  4 ++--
 4 files changed, 33 insertions(+), 39 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index bb3e926afd91..2a564bfd818c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1651,6 +1651,7 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
 		unsigned long start, unsigned long end);
 
 struct mmu_notifier_range;
+struct mmu_notifier;
 
 void free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
 		unsigned long end, unsigned long floor, unsigned long ceiling);
@@ -1660,7 +1661,7 @@ int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
 		   struct mmu_notifier_range *range,
 		   pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp);
 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
-	unsigned long *pfn);
+	unsigned long *pfn, struct mmu_notifier *subscription);
 int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address,
 		      unsigned long *pfn);
 int follow_phys(struct vm_area_struct *vma, unsigned long address,
diff --git a/mm/memory.c b/mm/memory.c
index 0db0c5e233fd..a27b9b9c22c2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4789,11 +4789,30 @@ int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
 }
 EXPORT_SYMBOL(follow_pte_pmd);
 
+static int __follow_pfn(struct vm_area_struct *vma, unsigned long address,
+			unsigned long *pfn)
+{
+	int ret = -EINVAL;
+	spinlock_t *ptl;
+	pte_t *ptep;
+
+	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
+		return ret;
+
+	ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
+	if (ret)
+		return ret;
+	*pfn = pte_pfn(*ptep);
+	pte_unmap_unlock(ptep, ptl);
+	return 0;
+}
+
 /**
  * follow_pfn - look up PFN at a user virtual address
  * @vma: memory mapping
  * @address: user virtual address
  * @pfn: location to store found PFN
+ * @subscription: mmu_notifier subscription for the mm @vma is part of
  *
  * Only IO mappings and raw PFN mappings are allowed. Note that callers must
  * ensure coherency with pte updates by using a &mmu_notifier to follow updates.
@@ -4805,21 +4824,12 @@ EXPORT_SYMBOL(follow_pte_pmd);
  * Return: zero and the pfn at @pfn on success, -ve otherwise.
  */
 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
-	unsigned long *pfn)
+	unsigned long *pfn, struct mmu_notifier *subscription)
 {
-	int ret = -EINVAL;
-	spinlock_t *ptl;
-	pte_t *ptep;
-
-	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
-		return ret;
+	if (WARN_ON(subscription->mm != vma->vm_mm))
+		return -EINVAL;
 
-	ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
-	if (ret)
-		return ret;
-	*pfn = pte_pfn(*ptep);
-	pte_unmap_unlock(ptep, ptl);
-	return 0;
+	return __follow_pfn(vma, address, pfn);
 }
 EXPORT_SYMBOL_GPL(follow_pfn);
 
@@ -4844,7 +4854,7 @@ int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address,
 	WARN_ONCE(1, "unsafe follow_pfn usage\n");
 	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
 
-	return follow_pfn(vma, address, pfn);
+	return __follow_pfn(vma, address, pfn);
 }
 EXPORT_SYMBOL(unsafe_follow_pfn);
 
diff --git a/mm/nommu.c b/mm/nommu.c
index 79fc98a6c94a..a1e178401146 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -111,27 +111,6 @@ unsigned int kobjsize(const void *objp)
 	return page_size(page);
 }
 
-/**
- * follow_pfn - look up PFN at a user virtual address
- * @vma: memory mapping
- * @address: user virtual address
- * @pfn: location to store found PFN
- *
- * Only IO mappings and raw PFN mappings are allowed.
- *
- * Returns zero and the pfn at @pfn on success, -ve otherwise.
- */
-int follow_pfn(struct vm_area_struct *vma, unsigned long address,
-	unsigned long *pfn)
-{
-	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
-		return -EINVAL;
-
-	*pfn = address >> PAGE_SHIFT;
-	return 0;
-}
-EXPORT_SYMBOL_GPL(follow_pfn);
-
 /**
  * unsafe_follow_pfn - look up PFN at a user virtual address
  * @vma: memory mapping
@@ -153,7 +132,11 @@ int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address,
 	WARN_ONCE(1, "unsafe follow_pfn usage\n");
 	add_taint(TAINT_USER, LOCKDEP_STILL_OK);
 
-	return follow_pfn(vma, address, pfn);
+	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
+		return -EINVAL;
+
+	*pfn = address >> PAGE_SHIFT;
+	return 0;
 }
 EXPORT_SYMBOL(unsafe_follow_pfn);
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 417f3d470c3e..6f6786524eff 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1891,7 +1891,7 @@ static int hva_to_pfn_remapped(struct kvm *kvm, struct vm_area_struct *vma,
 	unsigned long pfn;
 	int r;
 
-	r = follow_pfn(vma, addr, &pfn);
+	r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
 	if (r) {
 		/*
 		 * get_user_pages fails for VM_IO and VM_PFNMAP vmas and does
@@ -1906,7 +1906,7 @@ static int hva_to_pfn_remapped(struct kvm *kvm, struct vm_area_struct *vma,
 		if (r)
 			return r;
 
-		r = follow_pfn(vma, addr, &pfn);
+		r = follow_pfn(vma, addr, &pfn, &kvm->mmu_notifier);
 		if (r)
 			return r;
 
-- 
2.29.2

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

  parent reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-27 16:41 [PATCH v7 00/17] follow_pfn and other iomap races Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 01/17] drm/exynos: Stop using frame_vector helpers Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 02/17] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 03/17] misc/habana: Stop using frame_vector helpers Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 04/17] misc/habana: Use FOLL_LONGTERM for userptr Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 05/17] mm/frame-vector: Use FOLL_LONGTERM Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 06/17] media: videobuf2: Move frame_vector into media subsystem Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 07/17] mm: Close race in generic_access_phys Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 08/17] PCI: Obey iomem restrictions for procfs mmap Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 09/17] /dev/mem: Only set filp->f_mapping Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 10/17] resource: Move devmem revoke code to resource framework Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 11/17] sysfs: Support zapping of binary attr mmaps Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 12/17] PCI: Revoke mappings like devmem Daniel Vetter
2021-01-19  8:17   ` Daniel Vetter
2021-01-19 14:32     ` Greg Kroah-Hartman
2021-01-19 14:34       ` Daniel Vetter
2021-01-19 15:20         ` Greg Kroah-Hartman
2021-01-19 16:03           ` Daniel Vetter
2021-02-03 16:14             ` Daniel Vetter
2021-02-04 10:23               ` Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 13/17] mm: Add unsafe_follow_pfn Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 14/17] media/videobuf1|2: Mark follow_pfn usage as unsafe Daniel Vetter
2021-01-19 12:24   ` Hans Verkuil
2020-11-27 16:41 ` [PATCH v7 15/17] vfio/type1: Mark follow_pfn " Daniel Vetter
2020-11-27 16:41 ` [PATCH v7 16/17] kvm: pass kvm argument to follow_pfn callsites Daniel Vetter
2020-11-27 16:41 ` Daniel Vetter [this message]
2020-11-27 19:10   ` [PATCH v7 17/17] mm: add mmu_notifier argument to follow_pfn kernel test robot
2020-11-30 14:28     ` Daniel Vetter
2020-11-30 18:03       ` Nick Desaulniers
2021-01-12 13:24 ` [PATCH v7 00/17] follow_pfn and other iomap races Daniel Vetter
2021-01-12 13:28   ` Daniel Vetter
2021-01-12 20:57   ` Stephen Rothwell

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20201127164131.2244124-18-daniel.vetter@ffwll.ch \
    --to=daniel.vetter@ffwll.ch \
    --cc=akpm@linux-foundation.org \
    --cc=dan.j.williams@intel.com \
    --cc=daniel.vetter@intel.com \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=hch@infradead.org \
    --cc=jack@suse.cz \
    --cc=jgg@ziepe.ca \
    --cc=jglisse@redhat.com \
    --cc=jhubbard@nvidia.com \
    --cc=keescook@chromium.org \
    --cc=kvm@vger.kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-media@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-samsung-soc@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

dri-devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/dri-devel/0 dri-devel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dri-devel dri-devel/ https://lore.kernel.org/dri-devel \
		dri-devel@lists.freedesktop.org
	public-inbox-index dri-devel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.freedesktop.lists.dri-devel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git