Re: [PATCH 3/4] coredump: ELF-FDPIC: enable to omit anonymous shared memory

From: Robin Holt
Date: Wed Feb 21 2007 - 06:55:25 EST

On Wed, Feb 21, 2007 at 11:33:31AM +0000, David Howells wrote:
> Kawai, Hidehiro <hidehiro.kawai.ez@xxxxxxxxxxx> wrote:
> > Is coredump_setting_sem a global semaphore? If so, it prevents concurrent
> > core dumping.
> No, it doesn't. Look again:
> int do_coredump(long signr, int exit_code, struct pt_regs * regs)
> {
> <setup vars>
> >>>> down_read(&coredump_settings_sem);
> > Additionally, while some process is dumped, writing to
> > coredump_omit_anon_shared of unrelated process will be blocked.
> Yes, but that's probably reasonable. How likely (a) is a process to coredump,
> and (b) is a coredump to occur simultaneously with someone altering their
> settings?

And (c) altering the setting during a core dump going to produce an
unusable core dump. I don't think the locking is that difficult to add
and it just makes sense. I would venture a guess that it will take less
time to actually do the locking than to continue arguing it is not needed
when it clearly appears it is needed for even a small number of cases.

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