From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:32818) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dg604-0004qF-Os for qemu-devel@nongnu.org; Fri, 11 Aug 2017 05:13:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dg601-0003i1-J8 for qemu-devel@nongnu.org; Fri, 11 Aug 2017 05:13:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40260) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dg601-0003gu-9T for qemu-devel@nongnu.org; Fri, 11 Aug 2017 05:12:57 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B4BC27EAA1 for ; Fri, 11 Aug 2017 09:12:53 +0000 (UTC) Date: Fri, 11 Aug 2017 11:12:48 +0200 From: Eduardo Otubo Message-ID: <20170811091248.GA3051@vader> References: <20170728121040.631-1-otubo@redhat.com> <20170728121040.631-3-otubo@redhat.com> <20170802123356.GI4098@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170802123356.GI4098@redhat.com> Subject: Re: [Qemu-devel] [PATCH v3 2/6] seccomp: add obsolete argument to command line List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: qemu-devel@nongnu.org, thuth@redhat.com, pbonzini@redhat.com On Wed, Aug 02, 2017 at 01:33:56PM +0100, Daniel P. Berrange wrote: > On Fri, Jul 28, 2017 at 02:10:36PM +0200, Eduardo Otubo wrote: > > This patch introduces the argument [,obsolete=allow] to the `-sandbox on' > > option. It allows Qemu to run safely on old system that still relies on > > old system calls. > > > > Signed-off-by: Eduardo Otubo > > --- > > include/sysemu/seccomp.h | 4 +++- > > qemu-options.hx | 9 +++++++-- > > qemu-seccomp.c | 32 +++++++++++++++++++++++++++++++- > > vl.c | 16 +++++++++++++++- > > 4 files changed, 56 insertions(+), 5 deletions(-) > > > > diff --git a/include/sysemu/seccomp.h b/include/sysemu/seccomp.h > > index cfc06008cb..7a7bde246b 100644 > > --- a/include/sysemu/seccomp.h > > +++ b/include/sysemu/seccomp.h > > @@ -15,7 +15,9 @@ > > #ifndef QEMU_SECCOMP_H > > #define QEMU_SECCOMP_H > > > > +#define OBSOLETE 0x0001 > > Please namespace this - its far too generic a term to expose to other > source files. I'd suggest > > QEMU_SECCOMP_SET_OBSOLETE > > > -int seccomp_start(void); > > +int seccomp_start(uint8_t seccomp_opts); > > This only allows for 8 sets. Perhaps its enough, but I'd suggest > just using a uint32_t straight away. > > > diff --git a/qemu-options.hx b/qemu-options.hx > > index 746b5fa75d..54e492f36a 100644 > > --- a/qemu-options.hx > > +++ b/qemu-options.hx > > @@ -4004,13 +4004,18 @@ Old param mode (ARM only). > > ETEXI > > > > DEF("sandbox", HAS_ARG, QEMU_OPTION_sandbox, \ > > - "-sandbox Enable seccomp mode 2 system call filter (default 'off').\n", > > + "-sandbox on[,obsolete=allow] Enable seccomp mode 2 system call filter (default 'off').\n" \ > > + " obsolete: Allow obsolete system calls\n", > > QEMU_ARCH_ALL) > > STEXI > > -@item -sandbox @var{arg} > > +@item -sandbox @var{arg}[,obsolete=@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'. > > +@table @option > > +@item obsolete=@var{string} > > +Enable Obsolete system calls > > Lets explain this a bit more. > > E obsolete system calls that are provided by the kernel, but typically no > longer used by modern C library implementations. > > > +@end table > > ETEXI > > > > DEF("readconfig", HAS_ARG, QEMU_OPTION_readconfig, > > diff --git a/qemu-seccomp.c b/qemu-seccomp.c > > index f8877b07b5..c6a8b28260 100644 > > --- a/qemu-seccomp.c > > +++ b/qemu-seccomp.c > > @@ -31,6 +31,20 @@ struct QemuSeccompSyscall { > > uint8_t priority; > > }; > > > > +static const struct QemuSeccompSyscall obsolete[] = { > > + { SCMP_SYS(readdir), 255 }, > > + { SCMP_SYS(_sysctl), 255 }, > > + { SCMP_SYS(bdflush), 255 }, > > + { SCMP_SYS(create_module), 255 }, > > + { SCMP_SYS(get_kernel_syms), 255 }, > > + { SCMP_SYS(query_module), 255 }, > > + { SCMP_SYS(sgetmask), 255 }, > > + { SCMP_SYS(ssetmask), 255 }, > > + { SCMP_SYS(sysfs), 255 }, > > + { SCMP_SYS(uselib), 255 }, > > + { SCMP_SYS(ustat), 255 }, > > +}; > > + > > static const struct QemuSeccompSyscall blacklist[] = { > > { SCMP_SYS(reboot), 255 }, > > { SCMP_SYS(swapon), 255 }, > > @@ -56,7 +70,20 @@ static const struct QemuSeccompSyscall blacklist[] = { > > { SCMP_SYS(vserver), 255 }, > > }; > > > > -int seccomp_start(void) > > +static int is_obsolete(int syscall) > > +{ > > + unsigned int i = 0; > > + > > + for (i = 0; i < ARRAY_SIZE(obsolete); i++) { > > + if (syscall == obsolete[i].num) { > > + return 1; > > + } > > + } > > + > > + return 0; > > +} > > + > > +int seccomp_start(uint8_t seccomp_opts) > > { > > int rc = 0; > > unsigned int i = 0; > > @@ -69,6 +96,9 @@ int seccomp_start(void) > > } > > > > for (i = 0; i < ARRAY_SIZE(blacklist); i++) { > > + if ((seccomp_opts & OBSOLETE) && is_obsolete(blacklist[i].num)) { > > + continue; > > + } > > IMHO this is leading to a rather inefficient approach. Why not extend > QemuSeccompSyscall struct so that it has another field to list which > set it belongs to. Then you can do > > > static const struct QemuSeccompSyscall blacklist[] = { > { SCMP_SYS(reboot), 255, QEMU_SECCOMP_SET_DEFAULT }, > { SCMP_SYS(swapon), 255, QEMU_SECCOMP_SET_DEFAULT }, > .... > { SCMP_SYS(readdir), 255, QEMU_SECCOMP_SET_OBSOLETE }, > { SCMP_SYS(_sysctl), 255, QEMU_SECCOMP_SET_OBSOLETE }, > ... > > And then to process this you can do > > for (i = 0; i < ARRAY_SIZE(blacklist); i++) { > if (blacklist[i].set != QEMU_SECCOMP_SET_OBSOLETE && > blacklist[i].set & seccomp_opts) { > continue; I agree with all the rest except with this one. This would require a change on libseccomp itself. Not sure a change on the library would be suited for now. I'm working and reviewing all the comments today, so I'll try to post a new version later today. > } > > > > rc = seccomp_rule_add(ctx, SCMP_ACT_KILL, blacklist[i].num, 0); > > if (rc < 0) { > > goto seccomp_return; > > diff --git a/vl.c b/vl.c > > index 15b98800e9..cbe09c94af 100644 > > --- a/vl.c > > +++ b/vl.c > > @@ -271,6 +271,10 @@ static QemuOptsList qemu_sandbox_opts = { > > .name = "enable", > > .type = QEMU_OPT_BOOL, > > }, > > + { > > + .name = "obsolete", > > + .type = QEMU_OPT_STRING, > > + }, > > { /* end of list */ } > > }, > > }; > > @@ -1032,7 +1036,17 @@ static int parse_sandbox(void *opaque, QemuOpts *opts, Error **errp) > > { > > if (qemu_opt_get_bool(opts, "enable", false)) { > > #ifdef CONFIG_SECCOMP > > - if (seccomp_start() < 0) { > > + uint8_t seccomp_opts = 0x0000; > > + const char *value = NULL; > > + > > + value = qemu_opt_get(opts, "obsolete"); > > + if (value) { > > + if (strcmp(value, "allow") == 0) { > > + seccomp_opts |= OBSOLETE; > > + } > > + } > > IIUC, the values will all be booleans, so we should just use > > if (qemu_opt_get_bool(opts, "obsolete", false)) > seccomp_opts |= OBSOLETE; > > > + > > + if (seccomp_start(seccomp_opts) < 0) { > > error_report("failed to install seccomp syscall filter " > > "in the kernel"); > > return -1; > > Regards, > Daniel > -- > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| -- Eduardo Otubo Senior Software Engineer @ RedHat