20050303: Serious error in pqact in LDM through 6.2.1

Harry,

You're absolutely right.  pqact(1) shouldn't allow decoders to use 
the standard error stream if it's not connected to a logfile.

Thanks for the patch.  It'll be in the next release.

Must've felt good poking into code again.  :-)

Regards,
Steve Emmerson

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------- Original Message

>To: address@hidden
>From: Harry Edmon <address@hidden>
>Subject: Serious error in pqact in LDM through 6.2.1
>Organization: University of Washington
>Keywords: 200503031035.j23AZjv2005120 LDM 6.2.1 pqact

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There is a serious error in pqact in LDM through version 6.2.1.  In 
pqact there is code that closes stderr (aka unit 2) if the log file is 
not specified or if it is "-".  This makes unit 2 available for opening 
of files, pipe, etc.  The problem is when a EXEC or PIPE action is 
executed, whatever is open on unit 2 is inheritted by the forked 
program, which would use it as stderr.  This may result in programs 
writing error information into random LDM files!

My proposed solution is to remember if stderr was closed at the start of 
pqact, and in that case open stderr as /dev/null when invoking EXEC or 
PIPE actions.  Attached is a diff file for my patch to ldm version 6.2.1.

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*** pqact/pqact.c.orig  Wed Jan 26 13:35:21 2005
--- pqact/pqact.c       Thu Mar  3 01:59:30 2005
***************
*** 61,66 ****
--- 61,70 ----
  #define DEFAULT_PIPE_TIMEO 60
  #endif /* !DEFAULT_PIPE_TIMEO */
  int pipe_timeo = DEFAULT_PIPE_TIMEO;
+ /*
+  * Did we close stderr
+  */
+ int stderr_closed = 0;
  
  
  /*
***************
*** 331,338 ****
           */
          (void)fclose(stdin);
          (void)fclose(stdout);
!         if (NULL == logfname || 0 != strcmp(logfname, "-"))
                  (void)fclose(stderr);
  
          /*
           * Inform the "filel" module about the number of available file
--- 335,344 ----
           */
          (void)fclose(stdin);
          (void)fclose(stdout);
!         if (NULL == logfname || 0 != strcmp(logfname, "-")) {
                  (void)fclose(stderr);
+               stderr_closed = 1;
+       }
  
          /*
           * Inform the "filel" module about the number of available file
*** pqact/action.c.orig Mon Aug  9 07:46:01 2004
--- pqact/action.c      Thu Mar  3 02:10:45 2005
***************
*** 60,65 ****
--- 60,66 ----
       int argc, char **argv,
       const void *xprod, size_t xlen)
  {
+       extern stderr_closed;
          pid_t pid;
          int dontwait = 1; /* default is not to wait */
  
***************
*** 102,108 ****
                                  (void) close(fd);
                          }
                  }
!                 /* we leave fd 2 (stderr) alone... */
  
                  (void)close_all();
  
--- 103,120 ----
                                  (void) close(fd);
                          }
                  }
!                 /* we leave fd 2 (stderr) alone unless already closed  */
!               if (stderr_closed) {
!                       (void)close(2);
!                       {
!                               int fd = open("/dev/null", O_WRONLY);
!                               if(fd > 2)
!                               {
!                                       (void) dup2(fd, 2);
!                                       (void) close(fd);
!                               }
!                         }
!                 }
  
                  (void)close_all();
  
*** pqact/filel.c.orig  Mon Aug  9 12:11:12 2004
--- pqact/filel.c       Thu Mar  3 02:10:23 2005
***************
*** 878,883 ****
--- 878,884 ----
  static int
  pipe_open(fl_entry *entry, int argc, char **argv)
  {
+       extern stderr_closed;
          int ac = argc;
          char **av = argv;
          int pfd[2];
***************
*** 943,949 ****
                                  (void) close(fd);
                          }
                  }
!                 /* we leave stderr alone */
  
                  endpriv();
  
--- 944,961 ----
                                  (void) close(fd);
                          }
                  }
!                 /* we leave fd 2 (stderr) alone unless already closed  */
!               if (stderr_closed) {
!                       (void)close(2);
!                       {
!                               int fd = open("/dev/null", O_WRONLY);
!                               if(fd > 2)
!                               {
!                                       (void) dup2(fd, 2);
!                                       (void) close(fd);
!                               }
!                         }
!                 }
  
                  endpriv();
  

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------- End of Original Message