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Date: Tue, 16 Apr 2013 09:02:31 +0100
From: Justin Cormack <>
Subject: unexpected syscall failures

I noticed that in some places we assume some system calls will not fail,
one example being in nice that I was looking at the other day, but there
are others:

return setpriority(PRIO_PROCESS, 0, getpriority(PRIO_PROCESS, 0)+inc);

Now in Linux you can use security frameworks (eg type 2 seccomp) to make
any system call fail. Do we want to program defensively around these cases?
(In the case of seccomp I think most people use it to abort the program not
error, but you can).

I am inclined to think that if someone makes getpid fail they deserve
anything they get. I can't see any security issues, just some potentially
confusing behaviour, eg here nice might succeed (but set errno) if
getpriority fails. But testing does have downsides.


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