| Message ID | 20170728121040.631-3-otubo@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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 <otubo@redhat.com> > --- > 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 <arg> 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
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 <otubo@redhat.com> > > --- > > include/sysemu/seccomp.h | 4 +++- > > qemu-options.hx | 9 +++++++-- > > qemu-seccomp.c | 32 +++++++++++++++++++++++++++++++- > > vl.c | 16 +++++++++++++++- > > 4 files changed, 56 insertions(+), 5 deletions(-) > > @@ -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; Oh ignore this. I see from the next patch, we can't treat it as a boolean. We should however explicitly look for 'value == deny', and then reject all other values with an error message > > > + > > + if (seccomp_start(seccomp_opts) < 0) { > > error_report("failed to install seccomp syscall filter " > > "in the kernel"); > > return -1; Regards, Daniel
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 <otubo@redhat.com> > > --- > > 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 <arg> 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 :|
On Fri, Aug 11, 2017 at 11:12:48AM +0200, Eduardo Otubo wrote: > 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 <otubo@redhat.com> > > > --- > > > 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 <arg> 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. Huh ? QemuSeccompSyscall is a QEMU defined struct, and this is QEMU code. The change I describe here takes place before we even call libseccomp and doesn't affect any APIs we call in the future Regards, Daniel
On Fri, Aug 11, 2017 at 11:12:48AM +0200, Eduardo Otubo wrote: > 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 <otubo@redhat.com> > > > --- > > > 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 <arg> 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. Let me reply this before you do: My mistake, this structure model does not belong to libseccomp. My bad. So yeah, I can change it to optimize things here. Thanks for the idea :) > > > } > > > > > > > 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
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 + #include <seccomp.h> -int seccomp_start(void); +int seccomp_start(uint8_t seccomp_opts); #endif 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 <arg> 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 +@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; + } 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; + } + } + + if (seccomp_start(seccomp_opts) < 0) { error_report("failed to install seccomp syscall filter " "in the kernel"); return -1;
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 <otubo@redhat.com> --- include/sysemu/seccomp.h | 4 +++- qemu-options.hx | 9 +++++++-- qemu-seccomp.c | 32 +++++++++++++++++++++++++++++++- vl.c | 16 +++++++++++++++- 4 files changed, 56 insertions(+), 5 deletions(-)