[v3] Add seccomp argument filters for madvise, shmget, and shmctl

Signed-off-by: Namsun Ch'o <namnamc@airmail.cc>
---
Changes so far:
v1
  - Created argument filters for the madvise, shmget, and shmctl 
syscalls.
v1 -> v2
  - Added 5 new madvise flags which were present in the source code but 
not in
    the strace which I generated.
  - Added IP_CREAT|0600 to shmget, which Daniel Berrange pointed out was
    present in GTK2, which QEMU uses but does not call directly.
v2 -> v3
  - Replaced include asm/mman-common.h with sys/mman.h which is more 
proper.
  - Fixed a stupid typo where I had IP_CREAT instead of IPC_CREAT.
  - Removed the comma on the last entry of the madvise_flags array.
  - Removed one madvise flag (MADV_INVALID) which doesn't exist, 
apparently.

  qemu-seccomp.c | 58 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++---
  1 file changed, 55 insertions(+), 3 deletions(-)

      { SCMP_SYS(pselect6), 245 },
@@ -224,11 +225,9 @@ static const struct QemuSeccompSyscall 
seccomp_whitelist[] = {
      { SCMP_SYS(arch_prctl), 240 },
      { SCMP_SYS(mkdir), 240 },
      { SCMP_SYS(fchmod), 240 },
-    { SCMP_SYS(shmget), 240 },
      { SCMP_SYS(shmat), 240 },
      { SCMP_SYS(shmdt), 240 },
      { SCMP_SYS(timerfd_create), 240 },
-    { SCMP_SYS(shmctl), 240 },
      { SCMP_SYS(mlockall), 240 },
      { SCMP_SYS(mlock), 240 },
      { SCMP_SYS(munlock), 240 },
@@ -265,6 +264,59 @@ int seccomp_start(void)
          }
      }

+    /* madvise */
+    static const int madvise_flags[] = {
+        MADV_DODUMP,
+        MADV_DONTDUMP,
+        MADV_UNMERGEABLE,
+        MADV_WILLNEED,
+        MADV_DONTFORK,
+        MADV_DONTNEED,
+        MADV_HUGEPAGE,
+        MADV_MERGEABLE
+    };
+    for (i = 0; i < ARRAY_SIZE(madvise_flags); i++) {
+        rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(madvise), 
1,
+            SCMP_A2(SCMP_CMP_EQ, madvise_flags[i]));
+        if (rc < 0) {
+            goto seccomp_return;
+        }
+    }
+    rc = seccomp_syscall_priority(ctx, SCMP_SYS(madvise), 245);
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+
+    /* shmget */
+    rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(shmget), 2,
+        SCMP_A0(SCMP_CMP_EQ, IPC_PRIVATE),
+        SCMP_A2(SCMP_CMP_EQ, IPC_CREAT|0777));
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+    rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(shmget), 2,
+        SCMP_A0(SCMP_CMP_EQ, IPC_PRIVATE),
+        SCMP_A2(SCMP_CMP_EQ, IPC_CREAT|0600));
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+    rc = seccomp_syscall_priority(ctx, SCMP_SYS(shmget), 240);
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+
+    /* shmctl */
+    rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(shmctl), 2,
+        SCMP_A1(SCMP_CMP_EQ, IPC_RMID),
+        SCMP_A2(SCMP_CMP_EQ, 0));
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+    rc = seccomp_syscall_priority(ctx, SCMP_SYS(shmctl), 240);
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+
      rc = seccomp_load(ctx);

    seccomp_return: