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From: "fweimer at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug nptl/27896] New: mq_notify does not handle separately allocated
 thread attributes
Date: Fri, 21 May 2021 08:54:12 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D27896

            Bug ID: 27896
           Summary: mq_notify does not handle separately allocated thread
                    attributes
           Product: glibc
           Version: 2.34
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
          Assignee: unassigned at sourceware dot org
          Reporter: fweimer at redhat dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

mq_notify makes a shallow copy of pthread_attr_t here:

  if (notification->sigev_notify_attributes !=3D NULL)
    {
      /* The thread attribute has to be allocated separately.  */
      data.attr =3D (pthread_attr_t *) malloc (sizeof (pthread_attr_t));
      if (data.attr =3D=3D NULL)
        return -1;

      memcpy (data.attr, notification->sigev_notify_attributes,
              sizeof (pthread_attr_t));
    }

This introduces a potential for a use-after-free bug because the affinity m=
ask
has been separately allocated, since before the addition of mq_notify. (A
caller of mq_notify can call pthread_attr_destroy immediately after mq_noti=
fy
returns and before the new thread is created.)

Found through code inspection. No known application impact.

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