Tvheadend

Summary¶

I observed unexpected behavior using the properties (under Configuration / Recording / Digital Video Recorder Profiles / Miscellaneous Settings):

• pre-processor command
• post-processor-command
• post-remove command

Certain commands cause error messages in the log or even reproduceable segfaults.

Observed behavior¶

• sh -c '/bin/df -P -h /recordings >/config/.markers/recording-pre-process'
  causes
  [ ERROR] spawn: shift: usage: shift [ -n arg# ] [ -b block# ] prog...

• sh -c "/bin/df -P -h /recordings >/config/.markers/recording-pre-process"
  causes
  tvheadend[4243]: segfault at 7ffe162bb000 ip 00007f5919eb54e1 sp 00007ffe162b7518 error 4 in ld-musl-x86_64.so.1[7f5919e7b000+46000]

• bash -c '/bin/df -P -h /recordings >/config/.markers/recording-pre-process'
  causes
  [ ERROR] spawn: -P: -c: line 0: unexpected EOF while looking for matching `''
[ ERROR] spawn: -P: -c: line 1: syntax error: unexpected end of file

• bash -c "/bin/df -P -h /recordings | tee /config/.markers/recording-pre-process"
  causes
  segfault at fffffffffffffffe ip 000055db1f3d884b sp 00007fffcda939a0 error 7 in tvheadend[55db1f384000+158000]

Analysis¶

I found in dvr_rec.c and hts_str.c that the command is parsed and splitted. The processing of double quotes and spaces seems to cause the problems. I guess that single quotes (') and redirections (e.g. | < >) are not supported at all, not even wrapped in a shell string.

Expected behavior¶

No segfault, and one of:

• Support of arbitrary shell commands
• Documentation about the limitations (preferably as mouse-over description in the configuration)

Workaround¶

Create a shell script that contains the command with quoted arguments and redirections.