[Bug network/19074] New: Data race in _res_hconf_reorder_addrs

[Bug network/19074] New: Data race in _res_hconf_reorder_addrs

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19074

            Bug ID: 19074
           Summary: Data race in _res_hconf_reorder_addrs
           Product: glibc
           Version: 2.23
            Status: NEW
          Severity: normal
          Priority: P2
         Component: network
          Assignee: fweimer at redhat dot com
          Reporter: fweimer at redhat dot com
  Target Milestone: ---
             Flags: security-

_res_hconf_reorder_addrs contains an instance of the incorrect double-checked
locking idiom:

  /* Number of interfaces.  */
  static int num_ifs = -1;
  /* We need to protect the dynamic buffer handling.  */
  __libc_lock_define_initialized (static, lock);
…
  if (num_ifs <= 0)
    {
…
      /* Get lock.  */
      __libc_lock_lock (lock);

      /* Recheck, somebody else might have done the work by now.  */
      if (num_ifs <= 0)
…
          num_ifs = new_num_ifs;
        }

      __libc_lock_unlock (lock);

num_ifs needs to be accessed with acquire loads and a release store.

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From: "fweimer at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug network/19074] Data race in _res_hconf_reorder_addrs
Date: Tue, 06 Oct 2015 12:17:00 -0000
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https://sourceware.org/bugzilla/show_bug.cgi?id\x19074

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED

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[Bug network/19074] Data race in _res_hconf_reorder_addrs

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=19074

--- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "GNU C Library master sources".

The branch, master has been updated
       via  f463c7b1839e2df5da0cd1fb6fe197f982b68765 (commit)
      from  d95453ef5d9fccac44ab3d4a161d917e7ef6231f (commit)

Those revisions listed above that are new to this repository have
not appeared on any other notification email; so we list those
revisions in full, below.

- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f463c7b1839e2df5da0cd1fb6fe197f982b68765

commit f463c7b1839e2df5da0cd1fb6fe197f982b68765
Author: Florian Weimer <fweimer@redhat.com>
Date:   Wed Oct 14 16:19:24 2015 +0200

    Fix double-checked locking in _res_hconf_reorder_addrs [BZ #19074]

        [BZ #19074]
        * resolv/res_hconf.c (_res_hconf_reorder_addrs): Use atomics to
        load and store num_ifs.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog          |    6 ++++
 NEWS               |    5 ++-
 resolv/res_hconf.c |   70 ++++++++++++++++++++++++++++++++++++++++++++++------
 3 files changed, 71 insertions(+), 10 deletions(-)

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[Bug network/19074] Data race in _res_hconf_reorder_addrs

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19074

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #2 from Florian Weimer <fweimer at redhat dot com> ---
Fixed in 2.23.

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[Bug network/19074] Data race in _res_hconf_reorder_addrs

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=19074

Joseph Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |2.23

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