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authorEduardo Otubo <otubo@redhat.com>2017-03-13 22:16:01 +0100
committerEduardo Otubo <otubo@redhat.com>2017-09-15 10:15:06 +0200
commit995a226f880b807e05240e8752d6ce65679775be (patch)
tree52c583395208ab69f6deb0bed685aeb3eefefbe0
parent73a1e647256b09734ce64ef7a6001a0db03f7106 (diff)
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seccomp: add spawn argument to command line
This patch adds [,spawn=deny] argument to `-sandbox on' option. It blacklists fork and execve system calls, avoiding Qemu to spawn new threads or processes. Signed-off-by: Eduardo Otubo <otubo@redhat.com>
-rw-r--r--include/sysemu/seccomp.h1
-rw-r--r--qemu-options.hx9
-rw-r--r--qemu-seccomp.c4
-rw-r--r--vl.c16
4 files changed, 28 insertions, 2 deletions
diff --git a/include/sysemu/seccomp.h b/include/sysemu/seccomp.h
index 4a9e63c..3ab5fc4 100644
--- a/include/sysemu/seccomp.h
+++ b/include/sysemu/seccomp.h
@@ -18,6 +18,7 @@
#define QEMU_SECCOMP_SET_DEFAULT (1 << 0)
#define QEMU_SECCOMP_SET_OBSOLETE (1 << 1)
#define QEMU_SECCOMP_SET_PRIVILEGED (1 << 2)
+#define QEMU_SECCOMP_SET_SPAWN (1 << 3)
#include <seccomp.h>
diff --git a/qemu-options.hx b/qemu-options.hx
index 5c1b163..2b04b9f 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4018,6 +4018,7 @@ ETEXI
DEF("sandbox", HAS_ARG, QEMU_OPTION_sandbox, \
"-sandbox on[,obsolete=allow|deny][,elevateprivileges=allow|deny|children]\n" \
+ " [,spawn=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" \
@@ -4025,10 +4026,12 @@ DEF("sandbox", HAS_ARG, QEMU_OPTION_sandbox, \
" use 'elevateprivileges' to allow or deny QEMU process to elevate\n" \
" its privileges by blacklisting all set*uid|gid system calls.\n" \
" The value 'children' will deny set*uid|gid system calls for\n" \
- " main QEMU process but will allow forks and execves to run unprivileged\n",
+ " main QEMU process but will allow forks and execves to run unprivileged\n" \
+ " use 'spawn' to avoid QEMU to spawn new threads or processes by\n" \
+ " blacklisting *fork and execve\n",
QEMU_ARCH_ALL)
STEXI
-@item -sandbox @var{arg}[,obsolete=@var{string}][,elevateprivileges=@var{string}]
+@item -sandbox @var{arg}[,obsolete=@var{string}][,elevateprivileges=@var{string}][,spawn=@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'.
@@ -4037,6 +4040,8 @@ disable it. The default is 'off'.
Enable Obsolete system calls
@item elevateprivileges=@var{string}
Disable set*uid|gid system calls
+@item spawn=@var{string}
+Disable *fork and execve
@end table
ETEXI
diff --git a/qemu-seccomp.c b/qemu-seccomp.c
index 978d66b..f3878a5 100644
--- a/qemu-seccomp.c
+++ b/qemu-seccomp.c
@@ -78,6 +78,10 @@ static const struct QemuSeccompSyscall blacklist[] = {
{ SCMP_SYS(setresgid), QEMU_SECCOMP_SET_PRIVILEGED },
{ SCMP_SYS(setfsuid), QEMU_SECCOMP_SET_PRIVILEGED },
{ SCMP_SYS(setfsgid), QEMU_SECCOMP_SET_PRIVILEGED },
+ /* spawn */
+ { SCMP_SYS(fork), QEMU_SECCOMP_SET_SPAWN },
+ { SCMP_SYS(vfork), QEMU_SECCOMP_SET_SPAWN },
+ { SCMP_SYS(execve), QEMU_SECCOMP_SET_SPAWN },
};
diff --git a/vl.c b/vl.c
index d59b560..984db0c 100644
--- a/vl.c
+++ b/vl.c
@@ -280,6 +280,10 @@ static QemuOptsList qemu_sandbox_opts = {
.name = "elevateprivileges",
.type = QEMU_OPT_STRING,
},
+ {
+ .name = "spawn",
+ .type = QEMU_OPT_STRING,
+ },
{ /* end of list */ }
},
};
@@ -1083,6 +1087,18 @@ static int parse_sandbox(void *opaque, QemuOpts *opts, Error **errp)
}
}
+ value = qemu_opt_get(opts, "spawn");
+ if (value) {
+ if (g_str_equal(value, "deny")) {
+ seccomp_opts |= QEMU_SECCOMP_SET_SPAWN;
+ } else if (g_str_equal(value, "allow")) {
+ /* default value */
+ } else {
+ error_report("invalid argument for spawn");
+ return -1;
+ }
+ }
+
if (seccomp_start(seccomp_opts) < 0) {
error_report("failed to install seccomp syscall filter "
"in the kernel");