Messages in this thread | | | From | (Eric W. Biederman) | Date | Tue, 21 Feb 2017 11:30:56 +1300 | Subject | Re: [PATCH V2 1/2] exec: don't wait for zombie threads with cred_guard_mutex held |
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Oleg,
My apologies for not replying in-line but I think I can be clearer just saying what I think needs to be said.
Today cred_guard_mutex is part of making exec appear to be an atomic operation to ptrace and and proc. To make exec appear to be atomic we do need to take the mutex at the beginning and release it at the end of exec.
The semantics of exec appear atomic to ptrace_attach and to proc readers are necessary to ensure we use the proper process credentials in the event of a suid exec.
I believe making cred_guard_mutex per task is an option. Reducing the scope of cred_guard_mutex concerns me. There appear to be some fields like sighand that we currently expose in proc that might possibly be problematic. So I am not certain we protect enough things in our proc accessors.
Do you know if we can make cred_guard_mutex a per-task lock again?
Eric
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