[New-bugs-announce] [issue13022] _multiprocessing.recvfd() doesn't check that file descriptor was actually received

[David Watson]

New submission from David Watson <baikie at users.sourceforge.net>:

The function _multiprocessing.recvfd() calls recvmsg() and
expects to receive a file descriptor in an SCM_RIGHTS control
message, but doesn't check that such a control message is
actually present.  So if the sender sends data without an
accompanying file descriptor, recvfd() will the return the
integer value of the uninitialized CMSG_DATA() buffer.

The attached recvfd-check.diff checks for a complete control
message of the correct type, and raises RuntimeError if it isn't
there.  This matches the behaviour of the proposed pure-Python
implementation at issue #12981.

The patch includes a test case, but like the other recently-added
tests for the function, it isn't guarded against
multiprocessing.reduction being unavailable.  Issue #12981 has a
patch "skip_reduction.diff" (already in 3.3) to fix this, and I'm
attaching recvfd-skip-reduction-fix.diff to apply on top of it
and guard the new test case as well.

----------
components: Extension Modules
files: recvfd-check.diff
keywords: patch
messages: 144351
nosy: baikie
priority: normal
severity: normal
status: open
title: _multiprocessing.recvfd() doesn't check that file descriptor was actually received
type: behavior
versions: Python 2.7, Python 3.2, Python 3.3
Added file: http://bugs.python.org/file23214/recvfd-check.diff

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<http://bugs.python.org/issue13022>
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