On 11/28/19 7:55 AM, Pierre Labastie wrote:
Le 28/11/2019 à 13:43, Pierre Labastie a écrit :
Le 27/11/2019 à 17:40, Bruce Dubbs a écrit :
Restarting previous thread as a new discussion.
On 2019-11-26 14:56 -0600, Douglas R. Reno wrote:
On 2019-11-26 14:39, Bruce Dubbs wrote:
Also, I am running into an issue I haven't noticed before. On my
existing system if I try to log in as user lfs with .bash_profile
set,
it automatically starts bash and then puts it into the background.
# su - lfs
[1]+ Stopped su - lfs
# jobs
[1]+ Stopped su - lfs
# fg
su - lfs
lfs:~$
The rules in the book work OK as .bash_profile is not present when
we
initially change to user lfs and then we source
.bash_profile. That
works.
It could have something to do with PAM and su, but I'm not
sure. Has
anyone else seen this?
Yes I have, it's happening on Debian 10 and on LFS now. I'm not sure
what's causing it
I've seen this on LFS. Not sure the reason.
I've investigated this a bit. The problem is in su after pam is installed. I
rebuilt shadow using --without-libpam and copied that to /bin (ensuring it was
suid). The our 'su - lfs' then worked perfectly.
I did some initial trials to see if changing some of the /etc/pam.d/su
configuration items were causing the problem, but changing /etc/pam.d/su to:
auth required pam_permit.so
account required pam_permit.so
session required pam_permit.so
password required pam_permit.so
still causes putting 'su - lfs' in the background. This makes me think the
problem is in su, but it could be something in bash-5.
On debian (where I see this problem on a fresh install, but not on an old (but
updated) install), they use su from util-linux. So the problem might not be su.
Note that the bash startup files are the same in both debian installations.
Further investigating, I found that bash's version in debian sid is 5.0.11,
while it is 5.0.3 on debian 10, and 5.0 on lfs (point versions are just
available through patches, I think).
So, on an lfs VM, I rebuilt bash with all the patches applied (up to 5.0.11),
and now, "su - lfs" works OK...
If you want, I can prepare a consolidated patch and modify the book.
That would be good, but we still need to address it as a caution in
section 4.4 as some hosts have the problem.
Looking at the patches, one of the following may be our problem:
Patch-ID: bash50-005
In certain cases, bash optimizes out a fork() call too early and
prevents traps from running.
Patch-ID: bash50-007
Running `exec' when job control was disabled, even temporarily, but
after it had been initialized, could leave the terminal in the wrong
process group for the executed process.
I suspect patch 7 fixes our specific problem.
-- Bruce
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