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19 Oct 2022 04:25:31 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10504"; a="804256560" X-IronPort-AV: E=Sophos;i="5.95,196,1661842800"; d="scan'208";a="804256560" Received: from smile.fi.intel.com ([10.237.72.54]) by orsmga005.jf.intel.com with ESMTP; 19 Oct 2022 04:25:29 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.96) (envelope-from ) id 1ol7CR-009pTW-1C; Wed, 19 Oct 2022 14:25:27 +0300 Date: Wed, 19 Oct 2022 14:25:27 +0300 From: Andy Shevchenko To: Haakon Bugge Cc: Jane Chu , Petr Mladek , "rostedt@goodmis.org" , "senozhatsky@chromium.org" , "linux@rasmusvillemoes.dk" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , John Haxby Subject: Re: [PATCH] vsprintf: protect kernel from panic due to non-canonical pointer dereference Message-ID: References: <20221017191611.2577466-1-jane.chu@oracle.com> <5d987403-a7bf-8996-d639-c99edeaabcdf@oracle.com> <799e5390-2ff5-02b7-2df7-61198d5451e2@oracle.com> <198982F5-E94C-4F95-8197-FE69EFBA670F@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <198982F5-E94C-4F95-8197-FE69EFBA670F@oracle.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=aNdDxwWG; spf=none (imf28.hostedemail.com: domain of andriy.shevchenko@linux.intel.com has no SPF policy when checking 134.134.136.24) smtp.mailfrom=andriy.shevchenko@linux.intel.com; dmarc=fail reason="No valid SPF" header.from=intel.com (policy=none) ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1666178733; a=rsa-sha256; cv=none; b=VQXiizPgXAOjoKCCdeWc6kFnmtwarumo+xqzyC8U4w+jCo7wwXWzY24FLw3NvzoycLJUI/ ejFctHS8hgolVCqL/gS8tiEhTiMY/dQ0OIzgulPLRQ07W+GfvdG/gob7hry/e3dsuAFi2/ nkdDE974x1hLRqZLUMR87ao1hr1Inck= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666178733; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=iIM4CBFVhanTC2F6akCp1y0hbk3XQcbgynflKyCQs4A=; b=GnY0zWl5Pblt1jtqQYcrtOGbJbr9ekborFRKjLiJqXjw13P+W3somBRP/M6D0sMfWhG3tL vyYJ4oQMvYvZxh6hZ2paKa6lyCUsgX3M6dipXLV540chE2VTmd+Y66hqg4V0hV8Iasz40R Wbo2YpN4gzApOSEkj2DFlfnoX0D8ulQ= X-Stat-Signature: i7rg83enrbchcedxoybxbaoow5jtd6ne X-Rspamd-Queue-Id: 99F71C0007 Authentication-Results: imf28.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=aNdDxwWG; spf=none (imf28.hostedemail.com: domain of andriy.shevchenko@linux.intel.com has no SPF policy when checking 134.134.136.24) smtp.mailfrom=andriy.shevchenko@linux.intel.com; dmarc=fail reason="No valid SPF" header.from=intel.com (policy=none) X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1666178733-485389 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Oct 19, 2022 at 10:43:07AM +0000, Haakon Bugge wrote: > > On 18 Oct 2022, at 22:49, Andy Shevchenko wrote: > > On Tue, Oct 18, 2022 at 08:30:01PM +0000, Jane Chu wrote: ... > > Obviously, to see the crash. And let kernel _to crash_. Isn't it what we need > > to see a bug as early as possible? > > If you follow that argument, why doesn't the kernel crash when the pointer > is, e.g., a NULL pointer? According to you, shouldn't it crash a early as > possible in that case also? Because it is _special_. It's not just an invalid pointer. There may be very well good cases where we supply (valid!) NULL pointers to the printf(). -- With Best Regards, Andy Shevchenko