From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40176) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dqFvb-0005Rj-Fv for qemu-devel@nongnu.org; Fri, 08 Sep 2017 05:50:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dqFvW-0007m4-Nh for qemu-devel@nongnu.org; Fri, 08 Sep 2017 05:50:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59540) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dqFvW-0007kw-DV for qemu-devel@nongnu.org; Fri, 08 Sep 2017 05:50:18 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5C126C047B66 for ; Fri, 8 Sep 2017 09:50:17 +0000 (UTC) References: <20170908091027.9104-1-otubo@redhat.com> <20170908091027.9104-5-otubo@redhat.com> From: Thomas Huth Message-ID: <2ebb2804-a613-0942-ee9b-aa900093ac98@redhat.com> Date: Fri, 8 Sep 2017 11:50:12 +0200 MIME-Version: 1.0 In-Reply-To: <20170908091027.9104-5-otubo@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCHv5 4/5] seccomp: add spawn argument to command line List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Otubo , qemu-devel@nongnu.org On 08.09.2017 11:10, Eduardo Otubo wrote: > This patch adds [,spawn=deny] argument to `-sandbox on' option. It > blacklists fork and execve system calls, avoiding Qemu to spawn new > threads or processes. > > Signed-off-by: Eduardo Otubo > --- > include/sysemu/seccomp.h | 1 + > qemu-options.hx | 9 +++++++-- > qemu-seccomp.c | 12 ++++++++++++ > vl.c | 16 ++++++++++++++++ > 4 files changed, 36 insertions(+), 2 deletions(-) > > diff --git a/include/sysemu/seccomp.h b/include/sysemu/seccomp.h > index 4a9e63c7cd..3ab5fc4f61 100644 > --- a/include/sysemu/seccomp.h > +++ b/include/sysemu/seccomp.h > @@ -18,6 +18,7 @@ > #define QEMU_SECCOMP_SET_DEFAULT (1 << 0) > #define QEMU_SECCOMP_SET_OBSOLETE (1 << 1) > #define QEMU_SECCOMP_SET_PRIVILEGED (1 << 2) > +#define QEMU_SECCOMP_SET_SPAWN (1 << 3) > > #include > > diff --git a/qemu-options.hx b/qemu-options.hx > index 5c1b163fb5..2b04b9f170 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -4018,6 +4018,7 @@ ETEXI > > DEF("sandbox", HAS_ARG, QEMU_OPTION_sandbox, \ > "-sandbox on[,obsolete=allow|deny][,elevateprivileges=allow|deny|children]\n" \ > + " [,spawn=allow|deny]\n" \ > " Enable seccomp mode 2 system call filter (default 'off').\n" \ > " use 'obsolete' to allow obsolete system calls that are provided\n" \ > " by the kernel, but typically no longer used by modern\n" \ > @@ -4025,10 +4026,12 @@ DEF("sandbox", HAS_ARG, QEMU_OPTION_sandbox, \ > " use 'elevateprivileges' to allow or deny QEMU process to elevate\n" \ > " its privileges by blacklisting all set*uid|gid system calls.\n" \ > " The value 'children' will deny set*uid|gid system calls for\n" \ > - " main QEMU process but will allow forks and execves to run unprivileged\n", > + " main QEMU process but will allow forks and execves to run unprivileged\n" \ > + " use 'spawn' to avoid QEMU to spawn new threads or processes by\n" \ > + " blacklisting *fork and execve\n", > QEMU_ARCH_ALL) > STEXI > -@item -sandbox @var{arg}[,obsolete=@var{string}][,elevateprivileges=@var{string}] > +@item -sandbox @var{arg}[,obsolete=@var{string}][,elevateprivileges=@var{string}][,spawn=@var{string}] > @findex -sandbox > Enable Seccomp mode 2 system call filter. 'on' will enable syscall filtering and 'off' will > disable it. The default is 'off'. > @@ -4037,6 +4040,8 @@ disable it. The default is 'off'. > Enable Obsolete system calls > @item elevateprivileges=@var{string} > Disable set*uid|gid system calls > +@item spawn=@var{string} > +Disable *fork and execve > @end table > ETEXI > > diff --git a/qemu-seccomp.c b/qemu-seccomp.c > index 2bad16cafb..4c169febf8 100644 > --- a/qemu-seccomp.c > +++ b/qemu-seccomp.c > @@ -79,6 +79,10 @@ static const struct QemuSeccompSyscall blacklist[] = { > { SCMP_SYS(setresgid), 4, QEMU_SECCOMP_SET_PRIVILEGED }, > { SCMP_SYS(setfsuid), 4, QEMU_SECCOMP_SET_PRIVILEGED }, > { SCMP_SYS(setfsgid), 4, QEMU_SECCOMP_SET_PRIVILEGED }, > + /* spawn */ > + { SCMP_SYS(fork), 8, QEMU_SECCOMP_SET_SPAWN }, > + { SCMP_SYS(vfork), 8, QEMU_SECCOMP_SET_SPAWN }, > + { SCMP_SYS(execve), 8, QEMU_SECCOMP_SET_SPAWN }, > }; > > > @@ -109,6 +113,14 @@ int seccomp_start(uint32_t seccomp_opts) > } > > break; > + case QEMU_SECCOMP_SET_SPAWN: > + if (seccomp_opts & QEMU_SECCOMP_SET_SPAWN) { > + break; > + } else { > + continue; > + } > + Remove the above empty line? Anyway, it's somewhat ugly that you need a switch-case statement here at all. Couldn't you simply check it like this: if (!(seccomp_opts & blacklist[i].set)) { continue; } ? You then just have to invert the meaning of the QEMU_SECCOMP_SET_OBSOLETE bit in the second patch, so that this bit is treated in the same way as the others (i.e. use uint32_t seccomp_opts = QEMU_SECCOMP_SET_OBSOLETE; instead of uint32_t seccomp_opts = 0x00000; in vl.c in the second patch). Thomas