Add a new file descriptor type for IPC shared memory objects and use it to

implement shm_open(2) and shm_unlink(2) in the kernel:
- Each shared memory file descriptor is associated with a swap-backed vm
  object which provides the backing store.  Each descriptor starts off with
  a size of zero, but the size can be altered via ftruncate(2).  The shared
  memory file descriptors also support fstat(2).  read(2), write(2),
  ioctl(2), select(2), poll(2), and kevent(2) are not supported on shared
  memory file descriptors.
- shm_open(2) and shm_unlink(2) are now implemented as system calls that
  manage shared memory file descriptors.  The virtual namespace that maps
  pathnames to shared memory file descriptors is implemented as a hash
  table where the hash key is generated via the 32-bit Fowler/Noll/Vo hash
  of the pathname.
- As an extension, the constant 'SHM_ANON' may be specified in place of the
  path argument to shm_open(2).  In this case, an unnamed shared memory
  file descriptor will be created similar to the IPC_PRIVATE key for
  shmget(2).  Note that the shared memory object can still be shared among
  processes by sharing the file descriptor via fork(2) or sendmsg(2), but
  it is unnamed.  This effectively serves to implement the getmemfd() idea
  bandied about the lists several times over the years.
- The backing store for shared memory file descriptors are garbage
  collected when they are not referenced by any open file descriptors or
  the shm_open(2) virtual namespace.

Submitted by:	dillon, peter (previous versions)
Submitted by:	rwatson (I based this on his version)
Reviewed by:	alc (suggested converting getmemfd() to shm_open())

1 files changed, 56 insertions, 0 deletions

diff --git a/sys/security/mac_stub/mac_stub.c b/sys/security/mac_stub/mac_stub.c
index 50463a054217..165e7bbb540e 100644
--- a/sys/security/mac_stub/mac_stub.c
+++ b/sys/security/mac_stub/mac_stub.c
@@ -578,6 +578,53 @@ stub_posixsem_create(struct ucred *cred, struct ksem *ks,
 }
 
 static int
+stub_posixshm_check_mmap(struct ucred *cred, struct shmfd *shmfd,
+    struct label *shmlabel, int prot, int flags)
+{
+
+	return (0);
+}
+
+static int
+stub_posixshm_check_open(struct ucred *cred, struct shmfd *shmfd,
+    struct label *shmlabel)
+{
+
+	return (0);
+}
+
+static int
+stub_posixshm_check_stat(struct ucred *active_cred, struct ucred *file_cred,
+    struct shmfd *shmfd, struct label *shmlabel)
+{
+
+	return (0);
+}
+
+static int
+stub_posixshm_check_truncate(struct ucred *active_cred,
+    struct ucred *file_cred, struct shmfd *shmfd, struct label *shmlabel)
+{
+
+	return (0);
+}
+
+static int
+stub_posixshm_check_unlink(struct ucred *cred, struct shmfd *shmfd,
+    struct label *shmlabel)
+{
+
+	return (0);
+}
+
+static void
+stub_posixshm_create(struct ucred *cred, struct shmfd *shmfd,
+    struct label *shmlabel)
+{
+
+}
+
+static int
 stub_priv_check(struct ucred *cred, int priv)
 {
 
@@ -1550,6 +1597,15 @@ static struct mac_policy_ops stub_ops =
 	.mpo_posixsem_destroy_label = stub_destroy_label,
 	.mpo_posixsem_init_label = stub_init_label,
 
+	.mpo_posixshm_check_mmap = stub_posixshm_check_mmap,
+	.mpo_posixshm_check_open = stub_posixshm_check_open,
+	.mpo_posixshm_check_stat = stub_posixshm_check_stat,
+	.mpo_posixshm_check_truncate = stub_posixshm_check_truncate,
+	.mpo_posixshm_check_unlink = stub_posixshm_check_unlink,
+	.mpo_posixshm_create = stub_posixshm_create,
+	.mpo_posixshm_destroy_label = stub_destroy_label,
+	.mpo_posixshm_init_label = stub_init_label,
+
 	.mpo_priv_check = stub_priv_check,
 	.mpo_priv_grant = stub_priv_grant,