From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?utf-8?Q?Am=C3=A9rico?= Wang Date: Tue, 23 Nov 2010 15:23:55 +0000 Subject: Re: [PATCH v2] fs: select: fix information leak to userspace Message-Id: <20101123152355.GB3816@hack> List-Id: References: <1289421483-23907-1-git-send-email-segooon@gmail.com> <20101112120834.33062900.akpm@linux-foundation.org> <8D90F8B2-EA29-4EB9-9807-294CE0D5523B@dilger.ca> <20101114092533.GB5323@albatros> <20101114180643.593d19ac.akpm@linux-foundation.org> <1289848341.2607.125.camel@edumazet-laptop> <20101123140111.GA3816@hack> <4CEBD37E.5060107@bfs.de> In-Reply-To: <4CEBD37E.5060107@bfs.de> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: walter harms Cc: =?utf-8?Q?Am=C3=A9rico?= Wang , Eric Dumazet , Andrew Morton , Vasiliy Kulikov , Andreas Dilger , kernel-janitors@vger.kernel.org, Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Jakub Jelinek On Tue, Nov 23, 2010 at 03:45:18PM +0100, walter harms wrote: >Am 23.11.2010 15:01, schrieb Am=C3=A9rico Wang: >> On Mon, Nov 15, 2010 at 08:12:21PM +0100, Eric Dumazet wrote: >>> >>> In my understanding, gcc should initialize all holes (and other not >>> mentioned fields) with 0, even for automatic storage [C99 only mandates >>> this on static storage] >>> >>> I tested on x86_64 and this is the case, but could not find a definitive >>> answer in gcc documentation. >>> >>=20 >> Yeah, this is not clearly defined by C99 I think, but we can still >> find some clues in 6.2.6.1, Paragraph 6, >>=20 >> " >> When a value is stored in an object of structure or union type, >> including in a member object, the bytes of the object representation >> that correspond to any padding bytes take unspecified values. >> " >>=20 >> So we can't rely on the compiler to initialize the padding bytes >> too. >>=20 >hi all, >as we see this is not a question of c99. >Maybe we can convince the gcc people to make 0 padding default. That will = not solve the >problems for other compilers but when they claim "works like gcc" we can p= ress then to >support this also. I can imagine that this will close some other subtle le= aks also. > >People that still want a "undefined" (for what ever reason) can use an opt= ion to enable it >again (e.g. --no-zero-padding). Well, IMHO, the default behavior should be "undefined", thus "-fzero-padding" is needed. But, you know, I am not a compiler people at all. :) > >do anyone have a contact so we can forward that request ? > gcc@gcc.gnu.org ? --=20 Live like a child, think like the god. =20 -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" = in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html