From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48941) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dcsql-0007pf-LB for qemu-devel@nongnu.org; Wed, 02 Aug 2017 08:34:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dcsqh-0006el-Ht for qemu-devel@nongnu.org; Wed, 02 Aug 2017 08:34:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52472) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dcsqh-0006cz-91 for qemu-devel@nongnu.org; Wed, 02 Aug 2017 08:34:03 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2B8C9883C0 for ; Wed, 2 Aug 2017 12:34:02 +0000 (UTC) Date: Wed, 2 Aug 2017 13:33:56 +0100 From: "Daniel P. Berrange" Message-ID: <20170802123356.GI4098@redhat.com> Reply-To: "Daniel P. Berrange" References: <20170728121040.631-1-otubo@redhat.com> <20170728121040.631-3-otubo@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170728121040.631-3-otubo@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: Eduardo Otubo Cc: qemu-devel@nongnu.org, thuth@redhat.com, pbonzini@redhat.com 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; } > 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 :|