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seccomp: add obsolete argument to command line

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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>
This commit is contained in:
Eduardo Otubo 2017-03-01 23:17:29 +01:00
parent 1bd6152ae2
commit 2b716fa6d6
4 changed files with 53 additions and 5 deletions
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3
include/sysemu/seccomp.h
View File

@ -16,8 +16,9 @@
#define QEMU_SECCOMP_H
#define QEMU_SECCOMP_SET_DEFAULT (1 << 0)
#define QEMU_SECCOMP_SET_OBSOLETE (1 << 1)
#include <seccomp.h>
int seccomp_start(void);
int seccomp_start(uint32_t seccomp_opts);
#endif

12
qemu-options.hx
View File

@ -4017,13 +4017,21 @@ 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|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" \
" C library implementations.\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,

19
qemu-seccomp.c
View File

@ -55,9 +55,22 @@ static const struct QemuSeccompSyscall blacklist[] = {
{ SCMP_SYS(tuxcall), QEMU_SECCOMP_SET_DEFAULT },
{ SCMP_SYS(ulimit), QEMU_SECCOMP_SET_DEFAULT },
{ SCMP_SYS(vserver), QEMU_SECCOMP_SET_DEFAULT },
/* obsolete */
{ SCMP_SYS(readdir), QEMU_SECCOMP_SET_OBSOLETE },
{ SCMP_SYS(_sysctl), QEMU_SECCOMP_SET_OBSOLETE },
{ SCMP_SYS(bdflush), QEMU_SECCOMP_SET_OBSOLETE },
{ SCMP_SYS(create_module), QEMU_SECCOMP_SET_OBSOLETE },
{ SCMP_SYS(get_kernel_syms), QEMU_SECCOMP_SET_OBSOLETE },
{ SCMP_SYS(query_module), QEMU_SECCOMP_SET_OBSOLETE },
{ SCMP_SYS(sgetmask), QEMU_SECCOMP_SET_OBSOLETE },
{ SCMP_SYS(ssetmask), QEMU_SECCOMP_SET_OBSOLETE },
{ SCMP_SYS(sysfs), QEMU_SECCOMP_SET_OBSOLETE },
{ SCMP_SYS(uselib), QEMU_SECCOMP_SET_OBSOLETE },
{ SCMP_SYS(ustat), QEMU_SECCOMP_SET_OBSOLETE },
};
int seccomp_start(void)
int seccomp_start(uint32_t seccomp_opts)
{
int rc = 0;
unsigned int i = 0;
@ -70,6 +83,10 @@ int seccomp_start(void)
}
for (i = 0; i < ARRAY_SIZE(blacklist); i++) {
if (!(seccomp_opts & blacklist[i].set)) {
continue;
}
rc = seccomp_rule_add(ctx, SCMP_ACT_KILL, blacklist[i].num, 0);
if (rc < 0) {
goto seccomp_return;

24
vl.c
View File

@ -271,6 +271,10 @@ static QemuOptsList qemu_sandbox_opts = {
.name = "enable",
.type = QEMU_OPT_BOOL,
},
{
.name = "obsolete",
.type = QEMU_OPT_STRING,
},
{ /* end of list */ }
},
};
@ -1034,7 +1038,25 @@ 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) {
uint32_t seccomp_opts = QEMU_SECCOMP_SET_DEFAULT
| QEMU_SECCOMP_SET_OBSOLETE;
const char *value = NULL;
value = qemu_opt_get(opts, "obsolete");
if (value) {
if (g_str_equal(value, "allow")) {
seccomp_opts &= ~QEMU_SECCOMP_SET_OBSOLETE;
} else if (g_str_equal(value, "deny")) {
/* this is the default option, this if is here
* to provide a little bit of consistency for
* the command line */
} else {
error_report("invalid argument for obsolete");
return -1;
}
}
if (seccomp_start(seccomp_opts) < 0) {
error_report("failed to install seccomp syscall filter "
"in the kernel");
return -1;