[Bug 1824732] Re: iocsh crashes when dealing with NULL iocshArgPersistentString

[mdavidsaver via Core-talk <core-talk at aps.anl.gov>]

> it is still used in some support modules.

Can you link an example?  I'm interested in if/how NULL is handled.

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https://bugs.launchpad.net/bugs/1824732

Title:
  iocsh crashes when dealing with NULL iocshArgPersistentString

Status in EPICS Base:
  Triaged
Status in EPICS Base 3.15 series:
  Triaged
Status in EPICS Base 7.0 series:
  Triaged

Bug description:
  I was looking at the iocsh.cpp (@R7.0.2.1) code and realized that
  there's a bug when parsing command arguments of type
  iocshArgPersistentString. The code in cvtArg does the following:

     case iocshArgPersistentString:
          argBuf->sval = (char *) malloc(strlen(arg) + 1);
          if (argBuf->sval == NULL) {
              showError(filename, lineno, "Out of memory");
              return 0;
          }
          strcpy(argBuf->sval, arg);
          break;

  However, here 'arg' can be NULL, so 'strlen' can (will?) SEGFAULT. I
  was able to successfully trigger the issue. I don't know where this is
  used or who uses this functionality exactly.

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