From: Axel Rasmussen <axelrasmussen@google.com>
To: "Alexander Viro" <viro@zeniv.linux.org.uk>,
"Alexey Dobriyan" <adobriyan@gmail.com>,
"Andrea Arcangeli" <aarcange@redhat.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Anshuman Khandual" <anshuman.khandual@arm.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Chinwen Chang" <chinwen.chang@mediatek.com>,
"Huang Ying" <ying.huang@intel.com>,
"Ingo Molnar" <mingo@redhat.com>, "Jann Horn" <jannh@google.com>,
"Jerome Glisse" <jglisse@redhat.com>,
"Lokesh Gidra" <lokeshgidra@google.com>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Michal Koutný" <mkoutny@suse.com>,
"Michel Lespinasse" <walken@google.com>,
"Mike Kravetz" <mike.kravetz@oracle.com>,
"Mike Rapoport" <rppt@linux.vnet.ibm.com>,
"Nicholas Piggin" <npiggin@gmail.com>,
"Peter Xu" <peterx@redhat.com>, "Shaohua Li" <shli@fb.com>,
"Shawn Anastasio" <shawn@anastas.io>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Steven Price" <steven.price@arm.com>,
"Vlastimil Babka" <vbabka@suse.cz>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, Adam Ruprecht <ruprecht@google.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Cannon Matthews <cannonmatthews@google.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
David Rientjes <rientjes@google.com>,
Oliver Upton <oupton@google.com>
Subject: [PATCH v2 4/9] hugetlb/userfaultfd: Unshare all pmds for hugetlbfs when register wp
Date: Fri, 22 Jan 2021 13:29:21 -0800 [thread overview]
Message-ID: <20210122212926.3457593-5-axelrasmussen@google.com> (raw)
In-Reply-To: <20210122212926.3457593-1-axelrasmussen@google.com>
From: Peter Xu <peterx@redhat.com>
Huge pmd sharing for hugetlbfs is racy with userfaultfd-wp because
userfaultfd-wp is always based on pgtable entries, so they cannot be shared.
Walk the hugetlb range and unshare all such mappings if there is, right before
UFFDIO_REGISTER will succeed and return to userspace.
This will pair with want_pmd_share() in hugetlb code so that huge pmd sharing
is completely disabled for userfaultfd-wp registered range.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
---
fs/userfaultfd.c | 45 ++++++++++++++++++++++++++++++++++++
include/linux/mmu_notifier.h | 1 +
2 files changed, 46 insertions(+)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 894cc28142e7..2c6706ac2504 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -15,6 +15,7 @@
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/mm.h>
+#include <linux/mmu_notifier.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
@@ -1190,6 +1191,47 @@ static ssize_t userfaultfd_read(struct file *file, char __user *buf,
}
}
+/*
+ * This function will unconditionally remove all the shared pmd pgtable entries
+ * within the specific vma for a hugetlbfs memory range.
+ */
+static void hugetlb_unshare_all_pmds(struct vm_area_struct *vma)
+{
+#ifdef CONFIG_HUGETLB_PAGE
+ struct hstate *h = hstate_vma(vma);
+ unsigned long sz = huge_page_size(h);
+ struct mm_struct *mm = vma->vm_mm;
+ struct mmu_notifier_range range;
+ unsigned long address;
+ spinlock_t *ptl;
+ pte_t *ptep;
+
+ /*
+ * No need to call adjust_range_if_pmd_sharing_possible(), because
+ * we're going to operate on the whole vma
+ */
+ mmu_notifier_range_init(&range, MMU_NOTIFY_HUGETLB_UNSHARE,
+ 0, vma, mm, vma->vm_start, vma->vm_end);
+ mmu_notifier_invalidate_range_start(&range);
+ i_mmap_lock_write(vma->vm_file->f_mapping);
+ for (address = vma->vm_start; address < vma->vm_end; address += sz) {
+ ptep = huge_pte_offset(mm, address, sz);
+ if (!ptep)
+ continue;
+ ptl = huge_pte_lock(h, mm, ptep);
+ huge_pmd_unshare(mm, vma, &address, ptep);
+ spin_unlock(ptl);
+ }
+ flush_hugetlb_tlb_range(vma, vma->vm_start, vma->vm_end);
+ i_mmap_unlock_write(vma->vm_file->f_mapping);
+ /*
+ * No need to call mmu_notifier_invalidate_range(), see
+ * Documentation/vm/mmu_notifier.rst.
+ */
+ mmu_notifier_invalidate_range_end(&range);
+#endif
+}
+
static void __wake_userfault(struct userfaultfd_ctx *ctx,
struct userfaultfd_wake_range *range)
{
@@ -1448,6 +1490,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
vma->vm_flags = new_flags;
vma->vm_userfaultfd_ctx.ctx = ctx;
+ if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma))
+ hugetlb_unshare_all_pmds(vma);
+
skip:
prev = vma;
start = vma->vm_end;
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index b8200782dede..ff50c8528113 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -51,6 +51,7 @@ enum mmu_notifier_event {
MMU_NOTIFY_SOFT_DIRTY,
MMU_NOTIFY_RELEASE,
MMU_NOTIFY_MIGRATE,
+ MMU_NOTIFY_HUGETLB_UNSHARE,
};
#define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)
--
2.30.0.280.ga3ce27912f-goog
next prev parent reply other threads:[~2021-01-22 21:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-22 21:29 [PATCH 0/9] userfaultfd: add minor fault handling Axel Rasmussen
2021-01-22 21:29 ` [PATCH v2 1/9] hugetlb: Pass vma into huge_pte_alloc() Axel Rasmussen
2021-01-22 21:29 ` [PATCH v2 2/9] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled Axel Rasmussen
2021-01-22 21:29 ` [PATCH v2 3/9] mm/hugetlb: Move flush_hugetlb_tlb_range() into hugetlb.h Axel Rasmussen
2021-01-22 21:29 ` Axel Rasmussen [this message]
2021-01-22 21:29 ` [PATCH v2 5/9] userfaultfd: add minor fault registration mode Axel Rasmussen
2021-01-22 21:29 ` [PATCH v2 6/9] userfaultfd: disable huge PMD sharing for MINOR registered VMAs Axel Rasmussen
2021-01-22 21:29 ` [PATCH v2 7/9] userfaultfd: add UFFDIO_CONTINUE ioctl Axel Rasmussen
2021-01-22 21:29 ` [PATCH v2 8/9] userfaultfd: update documentation to describe minor fault handling Axel Rasmussen
2021-01-22 21:29 ` [PATCH v2 9/9] userfaultfd/selftests: add test exercising " Axel Rasmussen
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