Messages in this thread | | | Date | Tue, 10 Feb 2009 12:08:08 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH, for 2.6.29] ptrace: fix the usage of ptrace_fork() |
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On Mon, 9 Feb 2009 02:02:33 +0100 Oleg Nesterov <oleg@redhat.com> wrote:
> I noticed by pure accident we have ptrace_fork() and friends. This was > added by "x86, bts: add fork and exit handling", commit > bf53de907dfdaac178c92d774aae7370d7b97d20 > > I can't test this, ds_request_bts() returns -EOPNOTSUPP, but I strongly > believe this needs the fix. I think something like this program > > int main(void) > { > int pid = fork(); > > if (!pid) { > ptrace(PTRACE_TRACEME, 0, NULL, NULL); > kill(getpid(), SIGSTOP); > fork(); > } else { > struct ptrace_bts_config bts = { > .flags = PTRACE_BTS_O_ALLOC, > .size = 4 * 4096, > }; > > wait(NULL); > > ptrace(PTRACE_SETOPTIONS, pid, NULL, PTRACE_O_TRACEFORK); > ptrace(PTRACE_BTS_CONFIG, pid, &bts, sizeof(bts)); > ptrace(PTRACE_CONT, pid, NULL, NULL); > > sleep(1); > } > > return 0; > } > > should crash the kernel. > > If the task is traced by its natural parent ptrace_reparented() returns 0 > but we should clear ->btsxxx anyway. > > This is a minimal fix for 2.6.29, we need further cleanups imho. >
This changelog is all a bit tentative-sounding.
> > --- 6.29-rc3/kernel/fork.c~BTS_FIX 2009-01-29 01:13:55.000000000 +0100 > +++ 6.29-rc3/kernel/fork.c 2009-02-09 01:03:48.000000000 +0100 > @@ -1093,7 +1093,7 @@ static struct task_struct *copy_process( > #ifdef CONFIG_DEBUG_MUTEXES > p->blocked_on = NULL; /* not blocked yet */ > #endif > - if (unlikely(ptrace_reparented(current))) > + if (unlikely(current->ptrace)) > ptrace_fork(p, clone_flags); > > /* Perform scheduler related setup. Assign this task to a CPU. */
Can we please confirm that this patch is indeed correct and needed?
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