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[Colin King <1244627@xxxxxxxxxxxxxxxxxx>]

So enabling this consumes an extra sizeof(atomic_t) bytes per inode. Instrumenting the kernel with it enabled we see:

* To boot a system:

0.113 MB allocated + 23 x 4K slabs in iint_cache, total: 0.203 MB
consumed for ~1288 cached file entries.  

* Install kernel + headers:

0.401 MB allocated + 37 x 4K slabs in iint_cache, total: 0.547 MB
consumed for ~2072 cached file entries

* Build a kernel (as root, stress test):

12.945MB allocated + 1023 x 4K slabs in iint_cache, total: 16.941 MB
consumed for ~57344 cached file entries.

So, typically we are seeing ~310 bytes per cached IMA file entry
consumed in the iint_cache slab and misc IMA file metadata.

Looking at the file system benchmarks, IMA built in but not enabled does
impact ext2, ext3 performance, but other file systems seem to run w/o
any impact. I may re-test the ext2/ext3 and also look at why we are
seeing the impact on ext2, ext3 if we enabled IMA.

File system performance impact on IOZONE tests with IMA appraise
enabled:

http://kernel.ubuntu.com/~cking/ima/ima-appraise/html_out_ima_ext2
http://kernel.ubuntu.com/~cking/ima/ima-appraise/html_out_ima_ext3
http://kernel.ubuntu.com/~cking/ima/ima-appraise/html_out_ima_ext4
http://kernel.ubuntu.com/~cking/ima/ima-appraise/html_out_ima_xfs
http://kernel.ubuntu.com/~cking/ima/ima-appraise/html_out_ima_btrfs

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https://bugs.launchpad.net/bugs/1244627

Title:
  Please enable CONFIG_IMA in the ubuntu kernel

Status in “linux” package in Ubuntu:
  Fix Committed
Status in “linux” source package in Trusty:
  Fix Committed

Bug description:
  I would be doubly happy if this also went into the raring backport
  kernel.

  I chatted with apw and kees on #ubuntu-kernel earlier in the week.
  From a security engineer on our team:

  so I was mistaken. if CONFIG_IMA=y, the default policy is NULL unless
  you boot with ima_tcb=on. without ima_tcb=y, nothing is measured,
  nothing is audited, no performance/memory hit is incurred.

  Same is true for CONFIG_IMA_APPRAISE, except with the
  ima_appraise_tcb=on commandline parameter. ima appraise gives us the
  ability to sign binaries at installation time and check the signature
  at runtime.

  So we are asking that you enable CONFIG_IMA, but to not enable it via
  the kernel command line options. IMA would boot with an empty policy
  and should incur no overhead. Enterprising folks who want to run IMA
  can enable it in grub at their option.

  CONFIG_IMA=y

  and possibly:

  CONFIG_IMA_MEASURE_PCR_IDX=10
  CONFIG_IMA_AUDIT=y
  CONFIG_IMA_LSM_RULES=y

  -A

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