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Zanna
Zanna
03:01
@EliahKagan it's a pleasure, thanks for involving me :) :)
@EliahKagan cool! So the omission in my answer is not actually embarrassing!
At least, not too terribly
And it can be updated nicely
 
11 hours later…
Eliah Kagan
Eliah Kagan
13:54
@Zanna I had thought this form of --preserve-env might work for LD_ variables, too, but I think it does not.
Zanna
Zanna
14:05
oh hmm I didn't realise there was a special sudo thing with those variables
Eliah Kagan
Eliah Kagan
I don't think there is.
I think the dynamic loader unsets LD_PRELOAD when a dynamically linked setuid executable is run by a user who is not its owner.
Eliah Kagan
Eliah Kagan
14:24
This seems to happen even when the user running it is the owner.
Also, it seems not to be the dynamic loader that is doing it.
 
1 hour later…
Eliah Kagan
Eliah Kagan
15:30
@Zanna It is the dynamic loader.
I was thrown off by how the specific statically linked binary I tried (/bin/busybox) implements its own logic to unset LD_PRELOAD under some circumstances. 
ek@Cord:~$ cp /usr/bin/printenv .
ek@Cord:~$ LD_PRELOAD=/lib/x86_64-linux-gnu/libc.so.6 ./printenv LD_PRELOAD
/lib/x86_64-linux-gnu/libc.so.6
ek@Cord:~$ chmod u+s printenv
ek@Cord:~$ LD_PRELOAD=/lib/x86_64-linux-gnu/libc.so.6 ./printenv LD_PRELOAD
ek@Cord:~$
But --preserve-env=list does work to preserve variables that sudo sets even with -E. This appears broadly to be the case, and not to be specific to the semi-undocumented case of PATH. For example: 
ek@Cord:~$ SUDO_USER='Owls rule!' sudo -E printenv SUDO_USER
ek
ek@Cord:~$ SUDO_USER='Owls rule!' sudo --preserve-env=SUDO_USER printenv SUDO_USER
Owls rule!
Zanna
Zanna
hahaha
Eliah Kagan
Eliah Kagan
But it's because sudo is a setuid executable that LD_PRELOAD is removed from its environment before it actually runs. (sudo doesn't have a choice about that, except in the sense that it could have been provided as a statically linked executable instead.)

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