kernel-packages team mailing list archive

[Luis Henriques <luis.henriques@xxxxxxxxxxxxx>]

Andy, could you please confirm you're running the kernel in -proposed
(2.6.32-62.125)?  Because it looks like you're hitting the bug the fix
described above is supposed to fix.

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https://bugs.launchpad.net/bugs/1327300

Title:
  Regression in commit 8e4e453d548e3c24e9070eda23c52f210951b921

Status in “linux” package in Ubuntu:
  Invalid
Status in “linux” source package in Lucid:
  Fix Committed

Bug description:
  Phil Turnbull reported a problem with the Lucid (2.6.32) backport of
    futex: Always cleanup owner tid in unlock_pi
    commit: 8e4e453d548e3c24e9070eda23c52f210951b921

  In patches-2.6.32.tgz:patches/0003-futex-Always-cleanup-owner-tid-in-unlock_pi.$
  there is this change (ignoring whitespace changes):

          curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
  -
  -               if (curval == -EFAULT)
  +       if (curval)
                  ret = -EFAULT;

  which seems to change the behaviour of the function.

  The purpose of the return value of cmpxchg_futex_value_locked changed
  in

  37a9d912b24f96a0591 "futex: Sanitize cmpxchg_futex_value_locked API"

  which is not included in 2.6.32. This patch changes the return value to a
  status code, but in 2.6.32 the return value is the value of the futex or
  -EFAULT. With this backported patch, any futex with a non-zero value will
  return -EFAULT.

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