[PATCH v5 2/2] ima: Handle -ESTALE returned by ima_filter_rule_match()

[Mimi Zohar]

Hi Scott,

On Fri, 2022-10-28 at 16:36 +0800, Guozihua (Scott) wrote:
> 
> I managed to re-produce this issue with the help of the following two 
> scripts:
> 
> read_tmp_measurement.sh:
> > #!/bin/bash
> > 
> > while true
> > do
> >         cat /root/tmp.txt > /dev/null
> >         measurement=`cat /sys/kernel/security/ima/ascii_runtime_measurements | grep "tmp\.txt" | wc -l`
> >         if [ "${measurement}" == "1" ]; then
> >                 echo "measurement found"
> >                 exit 1
> >         fi
> > done
> 
> test.sh:
> > #!/bin/bash
> > 
> > echo "measure obj_user=system_u obj_role=object_r obj_type=unlabeled_t" > /sys/kernel/security/ima/policy
> > 
> > cat /root/tmp2.txt
> > measurement=`cat /sys/kernel/security/ima/ascii_runtime_measurements | grep "tmp2\.txt" | wc -l`
> > [ "$measurement" == "1" ] && echo "measurement for tmp2 found"
> > 
> > cat /root/tmp.txt
> > measurement=`cat /sys/kernel/security/ima/ascii_runtime_measurements | grep "tmp\.txt" | wc -l`
> > [ "$measurement" == "1" ] && echo "measurement for tmp found, preparation failed!" && exit 1
> > 
> > ./read_tmp_measurement.sh &
> > pid=$!
> > 
> > cd /usr/share/selinux/default
> > semodule -i clock.pp.bz2
> > semodule -r clock
> > 
> > kill ${pid}

Are you loading/unloading any selinux policy or specifically clock? If
specifically clock, what is special about it?

> I created two files tmp.txt and tmp2.txt, assign them with type 
> user_home_t and unlabeled_t respectively and then run test.sh.
> On a multi-core environment, I managed to reproduce this issue pretty 
> easily and tested that once the solution is merged, the issue stops 
> happening.

As I only see an IMA measurement policy rule being loaded for
"unlabeled_t" and not "user_home_t", should I assume that an IMA
measurement rule already exists for "user_home_t"?

thanks,

Mimi