Messages in this thread | | | Date | Mon, 8 Nov 2010 15:56:47 +0100 | From | Oleg Nesterov <> | Subject | Q: perf_event && task->ptrace_bps[] |
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Hello.
I am trying to understand the usage of hw-breakpoints in arch_ptrace(). ptrace_set_debugreg() and related code looks obviously racy. Nothing protects us against flush_ptrace_hw_breakpoint() called by the dying tracee. Afaics we can leak perf_event or use the already freed memory or both.
Am I missed something?
Looking into the git history, I don't even know which patch should be blamed (if I am right), there were too many changes. I noticed that 2ebd4ffb6d0cb877787b1e42be8485820158857e "perf events: Split out task search into helper" moved the PF_EXITING check from find_get_context(). This check coould help if sys_ptrace() races with SIGKILL, but it was racy anyway.
It is not clear to me what should be done. Looking more, I do not understand the scope of perf_event/ctx at all, sys_perf_event_open() looks wrong too, see the next email I am going to send.
Oleg.
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