strace can lie

Subject: strace can lie
From: Misha Dankov (Misha_DankovF9.N5037.Z2.FIDONET.ORG)
Date: Tue Dec 28 1999 - 03:51:32 CST

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Hello, all!

>> Any ideas how to get rid of this problem? It is nasty. It is
>> very nasty and makes strace unusable for anything
>> security-sensitive.

 dM> Unfortunately, as long as the information is fetched from
 dM> userland by userland via ptrace, with an opportunity for it to
 dM> change before the kernel uses it, there is no hope for
 dM> eliminating the race.

 dM> If you really feel ambitious, you could try to make Linux support
 dM> ktrace. :-)

  I beleive there is a workaround: one can assign RealTime Scheduler to
debugger process (sched_setscheduler (strace_pid, SCHED_FIFO, p)) so it will
preempt any of processess being debugged. Of course, scheduling priority of
strace should be higher than one of process if process works under RT
scheduler too.

SY, Misha. [Linux Unregistered User]

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