BACKPORT: FROMGIT: hugetlb/userfaultfd: unshare all pmds for hugetlbfs when register wp
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.
Link: https://lkml.kernel.org/r/20210218231206.15524-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Adam Ruprecht <ruprecht@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Cannon Matthews <cannonmatthews@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michal Koutn" <mkoutny@suse.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shawn Anastasio <shawn@anastas.io>
Cc: Steven Price <steven.price@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
(cherry picked from commit 267bda5c9993856b86f91a998df632b29cf517e2
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm)
Link: https://lore.kernel.org/patchwork/patch/1382208/
Conflicts:
mm/hugetlb.c
(CONFIG_CMA not CP'ed in this kernel. Manual rebase)
Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Bug: 160737021
Bug: 169683130
Change-Id: I99d541ce45aaf924fa912f00dafa4caefe307755
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 839a914..fdf4b17 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -17,6 +17,7 @@
#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>
@@ -1474,6 +1475,9 @@
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/hugetlb.h b/include/linux/hugetlb.h
index fd18a32..acdaf6c 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -160,6 +160,8 @@
unsigned long address, unsigned long end, pgprot_t newprot);
bool is_hugetlb_entry_migration(pte_t pte);
+void hugetlb_unshare_all_pmds(struct vm_area_struct *vma);
+
#else /* !CONFIG_HUGETLB_PAGE */
static inline void reset_vma_resv_huge_pages(struct vm_area_struct *vma)
@@ -233,6 +235,8 @@
BUG();
}
+static inline void hugetlb_unshare_all_pmds(struct vm_area_struct *vma) { }
+
#endif /* !CONFIG_HUGETLB_PAGE */
/*
* hugepages at page global directory. If arch support
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 867db6b..4c6d19a 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5006,3 +5006,52 @@
spin_unlock(&hugetlb_lock);
put_page(page);
}
+
+/*
+ * This function will unconditionally remove all the shared pmd pgtable entries
+ * within the specific vma for a hugetlbfs memory range.
+ */
+void hugetlb_unshare_all_pmds(struct vm_area_struct *vma)
+{
+ struct hstate *h = hstate_vma(vma);
+ unsigned long sz = huge_page_size(h);
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long address, start, end;
+ spinlock_t *ptl;
+ pte_t *ptep;
+
+ if (!(vma->vm_flags & VM_MAYSHARE))
+ return;
+
+ start = ALIGN(vma->vm_start, PUD_SIZE);
+ end = ALIGN_DOWN(vma->vm_end, PUD_SIZE);
+
+ if (start >= end)
+ return;
+
+ /*
+ * No need to call adjust_range_if_pmd_sharing_possible(), because
+ * we have already done the PUD_SIZE alignment.
+ */
+ mmu_notifier_invalidate_range_start(mm, start, end);
+ i_mmap_lock_write(vma->vm_file->f_mapping);
+ for (address = start; address < end; address += PUD_SIZE) {
+ unsigned long tmp = address;
+
+ ptep = huge_pte_offset(mm, address, sz);
+ if (!ptep)
+ continue;
+ ptl = huge_pte_lock(h, mm, ptep);
+ /* We don't want 'address' to be changed */
+ huge_pmd_unshare(mm, &tmp, ptep);
+ spin_unlock(ptl);
+ }
+ flush_hugetlb_tlb_range(vma, start, 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(mm, start, end);
+}
+