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[Frank Heimes <1597971@xxxxxxxxxxxxxxxxxx>]

** Also affects: linux
   Importance: Undecided
       Status: New

** Also affects: ubuntu-z-systems
   Importance: Undecided
       Status: New

** Changed in: ubuntu-z-systems
     Assignee: (unassigned) => Andy Whitcroft (apw)

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https://bugs.launchpad.net/bugs/1597971

Title:
  kernel: signal return with invalid floating-point control

Status in Linux:
  New
Status in Ubuntu on IBM z Systems:
  New
Status in linux package in Ubuntu:
  New

Bug description:
  Please backport:
  commit bcf4dd5f9ee096bd1510f838dd4750c35df4e38b
  Author: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
  Date:   Mon Jun 27 17:06:45 2016 +0200

      s390: fix test_fp_ctl inline assembly contraints
      
      The test_fp_ctl function is used to test if a given value is a valid
      floating-point control. The inline assembly in test_fp_ctl uses an
      incorrect constraint for the 'orig_fpc' variable. If the compiler
      chooses the same register for 'fpc' and 'orig_fpc' the test_fp_ctl()
      function always returns true. This allows user space to trigger
      kernel oopses with invalid floating-point control values on the
      signal stack.
      
      This problem has been introduced with git commit 4725c86055f5bbdcdf
      "s390: fix save and restore of the floating-point-control register"
      
      Cc: stable@xxxxxxxxxxxxxxx # v3.13+
      Reviewed-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
      Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

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