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Hallyn" , linux-man@vger.kernel.org, Kees Cook , Linux API , lkml , Andy Lutomirski , Jann Horn , Oleg Nesterov , Christian Brauner , "Eric W. Biederman" , Containers , Aleksa Sarai , Tyler Hicks , Akihiro Suda Subject: Re: [PATCH 2/2] seccomp.2: document userspace notification To: Tycho Andersen References: <20181213001106.15268-1-tycho@tycho.ws> <20181213001106.15268-3-tycho@tycho.ws> <2cea5fec-e73e-5749-18af-15c35a4bd23c@gmail.com> <20190301145310.GC7413@cisco> <052d73e2-c786-a760-f03a-a07b5772de5a@gmail.com> <20190301151937.GE7413@cisco> From: "Michael Kerrisk (man-pages)" Message-ID: <20ff6d08-d9ac-06d3-5702-d7de3cc17685@gmail.com> Date: Fri, 1 Mar 2019 17:02:05 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190301151937.GE7413@cisco> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/1/19 4:19 PM, Tycho Andersen wrote: > On Fri, Mar 01, 2019 at 04:16:27PM +0100, Michael Kerrisk (man-pages) wrote: >> Hello Tycho, >> >> On 3/1/19 3:53 PM, Tycho Andersen wrote: >>> On Thu, Feb 28, 2019 at 01:52:19PM +0100, Michael Kerrisk (man-pages) wrote: >>>>> +a notification will be sent to this fd. See "Userspace Notification" below for >>>> >>>> s/fd/file descriptor/ throughout please. >>> >>> Will do. >>> >>>>> +more details. >>>> >>>> I think the description here could be better worded as something like: >>>> >>>> SECCOMP_FILTER_FLAG_NEW_LISTENER >>>> Register a new filter, as usual, but on success return a >>>> new file descriptor that provides user-space notifications. >>>> When the filter returns SECCOMP_RET_USER_NOTIF, a notification >>>> will be provided via this file descriptor. The close-on-exec >>>> flag is automatically set on the new file descriptor. ... >>>> >>>>> .RE >>>>> .TP >>>>> .BR SECCOMP_GET_ACTION_AVAIL " (since Linux 4.14)" >>>>> @@ -606,6 +613,17 @@ file. >>>>> .TP >>>>> .BR SECCOMP_RET_ALLOW >>>>> This value results in the system call being executed. >>>>> +.TP >>>>> +.BR SECCOMP_RET_USER_NOTIF " (since Linux 4.21)" >>>> >>>> Please see the start of this hanging list in the manual page. >>>> Can you confirm that SECCOMP_RET_USER_NOTIF really is the lowest >>>> in the precedence order of all of the filter return values? >>> >>> Oh, no, I didn't realize it was in a particular order. I'll switch it. >> >> Just for my immediate education (I'm experimenting right now), >> where/how does it fit in the precedence order? > > In between RET_ERRNO and RET_TRACE; see include/uapi/linux/seccomp.h > for details. Confirmed by experiment :-). Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/