[Bug 1769848] Re: wodim no longer works from non-root accounts

[John Zaitseff]

The number of bytes being mmap()ed (12587008 bytes) may well be set in
/etc/wodim.conf, where the following line appears by default:

CDR_FIFOSIZE=12m

Commenting out this line seems to solve the immediate problem, as only
8192 bytes are now mmap()ed--but I have not tested it with a read CD-R
disc, as it seems to me that an 8kB FIFO buffer is a bit small!

After some testing (without any blank CD-Rs), it seems that
CDR_FIFOSIZE=7788k works, but 7789k does not.  I don't have anything
that looks relevant in /etc/sysctl.conf or /etc/sysctl.d/*.

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Title:
  wodim no longer works from non-root accounts

Status in cdrkit package in Ubuntu:
  New

Bug description:
  With the upgrade from Artful to Bionic (18.04 LTS), wodim no longer
  works for non-root users.  Given that the cdrkit package itself has
  not changed (version 9:1.1.11-3ubuntu2), the most likely culprit is in
  the Linux kernel (Bionic, currently linux-image-4.15.0-20-generic
  4.15.0-20.21).

  In particular, running "wodim -v -dao -audio -copy *.wav" as a non-
  root user under Bionic now generates the following; this previously
  worked correctly in Artful and prior releases of Ubuntu:

  TOC Type: 0 = CD-DA
  wodim: Operation not permitted. Warning: Cannot raise RLIMIT_MEMLOCK limits.
  wodim: Resource temporarily unavailable. Cannot get mmap for 12587008 Bytes on /dev/zero.

  The exit code is 11.

  Note that the user in question is a member of the cdrom group, and
  running "ls -la /dev/sr0" gives:

  brw-rw----+ 1 root cdrom 11, 0 May  8 18:39 /dev/sr0

  Attached is an strace of running the above command line.  I could not
  find any workaround by a reasonably quick search of the Internet.

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