Re: [PATCH v2 1/2] coredump: use task comm instead of (unknown)

From: Jiri Slaby
Date: Tue Jun 07 2011 - 14:35:18 EST

On 06/07/2011 08:16 PM, Oleg Nesterov wrote:
> On 06/07, Jiri Slaby wrote:
>> @@ -1631,7 +1631,7 @@ static int cn_print_exe_file(struct core_name *cn)
>> exe_file = get_mm_exe_file(current->mm);
>> if (!exe_file)
>> - return cn_printf(cn, "(unknown)");
>> + return cn_printf(cn, "%s (path unknown)", current->comm);
> Hmm. The patch itself looks fine to me.
> Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> But the code looks wrong.
> What if d_path() fails with, say, ENAMETOOLONG? do_coredump() doesn't
> expect an error code != ENOMEM. This is just ugly, I'll send the simple
> fix. Anyway, if we are changing cn_print_exe_file(), perhaps it makes
> sense to fallback if d_path fails too?

Ah, I see. Perhaps it should check '< 0' instead of '== -ENOMEM' and
print the error in that case?

> And, I am just noticed...
> for (p = path; *p; p++)
> if (*p == '/')
> *p = '!';
> Why??? I am not arguing, just curious.

In fact the reason is in the patch 2/2:
coredump: escape / in hostname and comm

Change every occurence of / in comm and hostname to !. If the process
changes its name to contain /, the core is not dumped (if the
directory tree doesn't exist like that). The same with hostname being
something like myhost/3. Fix this behaviour by using the escape loop
used in %E. (We extract it to a separate function.)

Now both with comm == myprocess/1 and hostname == myhost/1, the core
is dumped like (kernel.core_pattern='core.%p.%e.%h):

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