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From: "fweimer at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug stdio/27842] New: Race condition in _IO_FLAGS2_NEED_LOCK
 optimization
Date: Mon, 10 May 2021 19:24:13 +0000
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X-Bugzilla-Product: glibc
X-Bugzilla-Component: stdio
X-Bugzilla-Version: 2.34
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D27842

            Bug ID: 27842
           Summary: Race condition in _IO_FLAGS2_NEED_LOCK optimization
           Product: glibc
           Version: 2.34
            Status: NEW
          Severity: minor
          Priority: P3
         Component: stdio
          Assignee: unassigned at sourceware dot org
          Reporter: fweimer at redhat dot com
  Target Milestone: ---
             Flags: security-

flockfile uses a read-modify-write operation on _flags2 outside a lock regi=
on,
which can potentially clobber concurrent _flags2 updates performed under the
lock.

Found via code review, no reproducer known.

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