[Qemu-devel] [PATCH 5/6] seccomp: add resourcecontrol argument to command line

[Eduardo Otubo]

This patch adds [,resourcecontrol=deny] to `-sandbox on' option. It
blacklists all process affinity and scheduler priority system calls to
avoid any bigger of the process.

Signed-off-by: Eduardo Otubo <address@hidden>
---
 include/sysemu/seccomp.h |  1 +
 qemu-options.hx          |  9 ++++++---
 qemu-seccomp.c           | 28 ++++++++++++++++++++++++++++
 vl.c                     | 11 +++++++++++
 4 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/include/sysemu/seccomp.h b/include/sysemu/seccomp.h
index f1614d6514..c7003dd197 100644
--- a/include/sysemu/seccomp.h
+++ b/include/sysemu/seccomp.h
@@ -18,6 +18,7 @@
 #define OBSOLETE    0x0001
 #define PRIVILEGED  0x0010
 #define SPAWN       0x0100
+#define RESOURCECTL 0x1000
 
 #include <seccomp.h>
 
diff --git a/qemu-options.hx b/qemu-options.hx
index 3d612f0fd1..7192236dee 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4004,13 +4004,14 @@ Old param mode (ARM only).
 ETEXI
 
 DEF("sandbox", HAS_ARG, QEMU_OPTION_sandbox, \
-    "-sandbox 
on[,obsolete=allow][,elevateprivileges=allow|deny|children][,spawn=deny]  
Enable seccomp mode 2 system call filter (default 'off').\n" \
+    "-sandbox 
on[,obsolete=allow][,elevateprivileges=allow|deny|children][,spawn=deny][,resourcecontrol=deny]
  Enable seccomp mode 2 system call filter (default 'off').\n" \
     "                obsolete: Allow obsolete system calls\n"
     "                elevateprivileges: allows or denies Qemu process to 
elevate its privileges by blacklisting all set*uid|gid system calls. 'children' 
will deny set*uid|gid system calls for main Qemu process but will allow forks 
and execves to run unprivileged\n"
-    "                spawn: avoids Qemu to spawn new threads or processes by 
blacklisting *fork and execve\n",
+    "                spawn: avoids Qemu to spawn new threads or processes by 
blacklisting *fork and execve\n"
+    "                resourcecontrol: disable process affinity and schedular 
priority\n",
     QEMU_ARCH_ALL)
 STEXI
address@hidden -sandbox @var{arg}[,address@hidden,address@hidden,address@hidden
address@hidden -sandbox 
@var{arg}[,address@hidden,address@hidden,address@hidden,address@hidden
 @findex -sandbox
 Enable Seccomp mode 2 system call filter. 'on' will enable syscall filtering 
and 'off' will
 disable it.  The default is 'off'.
@@ -4021,6 +4022,8 @@ Enable Obsolete system calls
 Disable set*uid|gid systema calls
 @item address@hidden
 Disable *fork and execve
address@hidden address@hidden
+Disable process affinity and schedular priority
 @end table
 ETEXI
 
diff --git a/qemu-seccomp.c b/qemu-seccomp.c
index 22a093ca1b..95c8e31d1a 100644
--- a/qemu-seccomp.c
+++ b/qemu-seccomp.c
@@ -31,6 +31,19 @@ struct QemuSeccompSyscall {
     uint8_t priority;
 };
 
+static const struct QemuSeccompSyscall resourcecontrol_syscalls[] = {
+    { SCMP_SYS(getpriority), 255 },
+    { SCMP_SYS(setpriority), 255 },
+    { SCMP_SYS(sched_setparam), 255 },
+    { SCMP_SYS(sched_getparam), 255 },
+    { SCMP_SYS(sched_setscheduler), 255 },
+    { SCMP_SYS(sched_getscheduler), 255 },
+    { SCMP_SYS(sched_setaffinity), 255 },
+    { SCMP_SYS(sched_getaffinity), 255 },
+    { SCMP_SYS(sched_get_priority_max), 255 },
+    { SCMP_SYS(sched_get_priority_min), 255 },
+};
+
 static const struct QemuSeccompSyscall spawn_syscalls[] = {
     { SCMP_SYS(fork), 255 },
     { SCMP_SYS(vfork), 255 },
@@ -158,6 +171,21 @@ int seccomp_start(uint8_t seccomp_opts)
         }
     }
 
+    if (seccomp_opts & RESOURCECTL) {
+        for (i = 0; i < ARRAY_SIZE(resourcecontrol_syscalls); i++) {
+            rc = seccomp_rule_add(ctx, SCMP_ACT_KILL,
+                                          resourcecontrol_syscalls[i].num, 0);
+            if (rc < 0) {
+                goto seccomp_return;
+            }
+            rc = seccomp_syscall_priority(ctx, resourcecontrol_syscalls[i].num,
+                                          
resourcecontrol_syscalls[i].priority);
+            if (rc < 0) {
+                goto seccomp_return;
+            }
+        }
+    }
+
     rc = seccomp_load(ctx);
 
   seccomp_return:
diff --git a/vl.c b/vl.c
index ae3fa8b139..d9d4b025b9 100644
--- a/vl.c
+++ b/vl.c
@@ -284,6 +284,10 @@ static QemuOptsList qemu_sandbox_opts = {
             .name = "spawn",
             .type = QEMU_OPT_STRING,
         },
+        {
+            .name = "resourcecontrol",
+            .type = QEMU_OPT_STRING,
+        },
         { /* end of list */ }
     },
 };
@@ -1076,6 +1080,13 @@ static int parse_sandbox(void *opaque, QemuOpts *opts, 
Error **errp)
             }
         }
 
+        value = qemu_opt_get(opts, "resourcecontrol");
+        if (value) {
+            if (strcmp(value, "deny") == 0) {
+                seccomp_opts |= RESOURCECTL;
+            }
+        }
+
         if (seccomp_start(seccomp_opts) < 0) {
             error_report("failed to install seccomp syscall filter "
                          "in the kernel");
-- 
2.13.3