Created attachment 601257 [details]
Email received when I run "crontest.sh" from cron

Description of problem:

I have a cron job that runs once a day to identify and purge some duplicate files. It emits one line to stdout per file it deletes.  The output mailed to me by cron preiodically includes lumps of binary data.  

To test, I created a much simpler job that simply echo's a couple of hundred lines of text. This works as expected as long as there is no delay between the lines being echo'd.  If I include a usleep 100000 between each line, I get the same binary junk included as in my real job's output.


Version-Release number of selected component (if applicable):

cronie-1.4.8-11.fc17.x86_64
cronie-1.4.8-10.fc16.x86_64


How reproducible:

Completely.

Steps to Reproduce:

1. Schedule a job with cron that outputs a reasonable amount to stdout, with delays between each line.  I used the following "crontest.sh":

#! /bin/bash
limit=200
delay=100000
for l in `seq -w 1 $limit`; do
    echo "This is line number $l of $limit ... Something fox, something dog."
    usleep $delay
done

2. Receive bad output by mail.

  
Actual results:

(Mail received from the script above attached).

The 58th line output includes a null byte part way through (in place of the "o" in "of 200") and is followed by a block of binary data after which the 58th line completes from the "o" that was mangled earlier and normal output resumes.

Line 121 of the output next shows the same corruption (but one character further in).  And again at line 184.


Expected results:

Unmangled lines of text in the output mailed by cron.


Additional info:

The binary data includes a small number of tantalising strings: "Linux", "seshat.verelanthe.lan" (the machine's hostname), and "3.4.6-2.fc17.x86_64" (the version of the running kernel).

Running the test script and piping its output into mail does not show any problems.