Messages in this thread | | | From | Linus Torvalds <> | Date | Mon, 7 Dec 2020 10:40:11 -0800 | Subject | Re: [PATCH 3/3] exec: Transform exec_update_mutex into a rw_semaphore |
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On Mon, Dec 7, 2020 at 1:10 AM Peter Zijlstra <peterz@infradead.org> wrote: > > > PeterZ, is there something I'm missing? > > Like this? > > https://lkml.kernel.org/r/20200828123720.GZ1362448@hirez.programming.kicks-ass.net
Yes, except I think you should remove the old ptrace_may_access() check.
Because otherwise we'll just end up having KCSAN complain about the unlocked optimistic accesses or something like that.
So do the perfmon_capable() check early - it doesn't need the exec_update_mutex - and then just do the ptrace_may_access() one late.
I don't see any point at all in checking privileges twice, and I do see real downsides. Not just that KCSAN issue, but also lack of coverage (ie the second check will then effectively never be tested, which is bad too).
Linus
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