From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with ESMTP id 6F29D6B0023 for ; Fri, 6 May 2011 02:01:39 -0400 (EDT) Received: by bwz17 with SMTP id 17so3744847bwz.14 for ; Thu, 05 May 2011 23:01:36 -0700 (PDT) Message-ID: <4DC38EBD.5060300@suse.cz> Date: Fri, 06 May 2011 08:01:33 +0200 From: Jiri Slaby MIME-Version: 1.0 Subject: Re: [PATCH 1/1] coredump: use task comm instead of (unknown) References: <4DC0FFAB.1000805@gmail.com> <1304494354-21487-1-git-send-email-jslaby@suse.cz> <20110505150601.a4457970.akpm@linux-foundation.org> In-Reply-To: <20110505150601.a4457970.akpm@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, jirislaby@gmail.com, Alan Cox , Al Viro , Andi Kleen , John Stultz , Oleg Nesterov Jiri Slaby Ccing Oleg. On 05/06/2011 12:06 AM, Andrew Morton wrote: > On Wed, 4 May 2011 09:32:34 +0200 > Jiri Slaby wrote: > >> If we don't know the file corresponding to the binary (i.e. exe_file >> is unknown), use "task->comm (path unknown)" instead of simple >> "(unknown)" as suggested by ak. >> >> The fallback is the same as %e except it will append "(path unknown)". >> >> Signed-off-by: Jiri Slaby >> Cc: Alan Cox >> Cc: Al Viro >> Cc: Andi Kleen >> --- >> fs/exec.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/fs/exec.c b/fs/exec.c >> index 5ee7562..0a4d281 100644 >> --- a/fs/exec.c >> +++ b/fs/exec.c >> @@ -1555,7 +1555,7 @@ 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); >> >> pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY); >> if (!pathbuf) { > > Direct access to current->comm is racy since we added > prctl(PR_SET_NAME). > > Hopefully John Stultz will soon be presenting us with a %p modifier for > displaying task_struct.comm. Then just make sure, you won't nest alloc_lock (task_lock) into siglock. > But we should get this settled pretty promptly as this is a form of > userspace-visible API. Use get_task_comm() for now. I thought about using get_task_comm, but was not sure, if it is safe to task_lock() at that place. Note that this is copied from %e. > Also, there's nothing which prevents userspace from rewriting > task->comm to something which contains slashes (this seems bad). If > that is done, your patch will do Bad Things - it should be modified to > use cn_print_exe_file()'s slash-overwriting codepath. %E (cn_print_exe_file) does exactly what %e (format_corename) does. So if this is really broken in the two ways, we should fix both the old %e and the new %E. I'm not sure whether at this point when the task is being killed and dumped, it can still change comm? For the slashes, I agree. That should be fixed in both cases. thanks, -- js suse labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org