[Bug nptl/14744] New: kill -32 $pid or kill -33 $pid on a process cancels a random thread

["bugdal at aerifal dot cx" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14744

             Bug #: 14744
           Summary: kill -32 $pid or kill -33 $pid on a process cancels a
                    random thread
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: minor
          Priority: P2
         Component: nptl
        AssignedTo: unassigned@sourceware.org
        ReportedBy: bugdal@aerifal.cx
                CC: drepper.fsp@gmail.com
    Classification: Unclassified


Signals 32 and 33 are used internally by NPTL. There's nothing wrong with this,
as they are not advertised as being available to applications (SIGRTMIN shows
up as 34 in multi-threaded applications, if I recall). However, if an outside
process sends these signals, the target process acts on the signal as if it
were a cancellation request for whichever thread happened to receive the
signal. This could cause severe breakage and data corruption in applications
which are not written to use cancellation and lack cleanup handlers.

I am unsure whether the impact is limited to user error (issuing the kill
command manually) or could arise in other ways. In any case, for robustness, I
think the signal handler should be a no-op unless pthread_cancel was really
called in the application.

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