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[Bug 1549601] Re: [Hyper-V] x86, pageattr: prevent overflow in slow_virt_to_phys() for X86_PAE

 

This bug is awaiting verification that the kernel in -proposed solves
the problem. Please test the kernel and update this bug with the
results. If the problem is solved, change the tag 'verification-needed-
trusty' to 'verification-done-trusty'.

If verification is not done by 5 working days from today, this fix will
be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how
to enable and use -proposed. Thank you!


** Tags added: verification-needed-trusty

** Tags added: verification-needed-wily

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https://bugs.launchpad.net/bugs/1549601

Title:
  [Hyper-V] x86,pageattr: prevent overflow in slow_virt_to_phys() for
  X86_PAE

Status in linux package in Ubuntu:
  Fix Committed
Status in linux source package in Trusty:
  Fix Committed
Status in linux source package in Wily:
  Fix Committed
Status in linux source package in Xenial:
  Fix Committed

Bug description:
  https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d1cd1210834649ce1ca6bafe5ac25d2f40331343

  x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE
  pte_pfn() returns a PFN of long (32 bits in 32-PAE), so "long <<
  PAGE_SHIFT" will overflow for PFNs above 4GB.

  Due to this issue, some Linux 32-PAE distros, running as guests on Hyper-V,
  with 5GB memory assigned, can't load the netvsc driver successfully and
  hence the synthetic network device can't work (we can use the kernel parameter
  mem=3000M to work around the issue).

  Cast pte_pfn() to phys_addr_t before shifting.

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References