From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 13 Dec 2018 04:16:46 -0800 From: Matthew Wilcox Subject: Re: [RFC PATCH v1 0/5] Add support for O_MAYEXEC Message-ID: <20181213121645.GN6830@bombadil.infradead.org> References: <20181212081712.32347-1-mic@digikod.net> <20181213030228.GM6830@bombadil.infradead.org> <1544699060.6703.11.camel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1544699060.6703.11.camel@linux.ibm.com> To: Mimi Zohar Cc: =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= , linux-kernel@vger.kernel.org, Al Viro , James Morris , Jonathan Corbet , Kees Cook , Matthew Garrett , Michael Kerrisk , =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= , Philippe =?iso-8859-1?Q?Tr=E9buchet?= , Shuah Khan , Thibaut Sautereau , Vincent Strubel , Yves-Alexis Perez , kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org List-ID: On Thu, Dec 13, 2018 at 06:04:20AM -0500, Mimi Zohar wrote: > > I don't have a problem with the concept, but we're running low on O_ bits. > > Does this have to be done before the process gets a file descriptor, > > or could we have a new syscall? Since we're going to be changing the > > interpreters anyway, it doesn't seem like too much of an imposition to > > ask them to use: > > > > int verify_for_exec(int fd) > > > > instead of adding an O_MAYEXEC. > > The indication needs to be set during file open, before the open > returns to the caller.  This is the point where ima_file_check() > verifies the file's signature.  On failure, access to the file is > denied. I understand that's what happens today, but do we need to do it that way? There's no harm in the interpreter having an fd to a file if it knows not to execute it. This is different from a program opening a file and having the LSM deny access to it because it violates the security model.