Plug leak in m_unshare.

m_unshare passes on the source mbuf's flags as-is to m_getcl and this
results in a leak if the flags include M_NOFREE.  The fix is to clear
the bits not listed in M_COPYALL before calling m_getcl.  M_RDONLY
should probably be filtered out too but that's outside the scope of this
fix.

Add assertions in the zone_mbuf and zone_pack ctors to catch similar
bugs.

Update netmap_get_mbuf to not pass M_NOFREE to m_getcl.  It's not clear
what the original code was trying to do but it's likely incorrect.
Updated code is no different functionally but it avoids the newly added
assertions.

Reviewed by:	gnn@
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D5698

3 files changed, 6 insertions, 3 deletions

diff --git a/sys/dev/netmap/netmap_generic.c b/sys/dev/netmap/netmap_generic.c
index bc5b452..9129960 100644
--- a/sys/dev/netmap/netmap_generic.c
+++ b/sys/dev/netmap/netmap_generic.c
@@ -129,8 +129,9 @@ static inline struct mbuf *
 netmap_get_mbuf(int len)
 {
 	struct mbuf *m;
-	m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR | M_NOFREE);
+	m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
 	if (m) {
+		m->m_flags |= M_NOFREE;	/* XXXNP: Almost certainly incorrect. */
 		m->m_ext.ext_arg1 = m->m_ext.ext_buf; // XXX save
 		m->m_ext.ext_free = (void *)netmap_default_mbuf_destructor;
 		m->m_ext.ext_type = EXT_EXTREF;
diff --git a/sys/kern/kern_mbuf.c b/sys/kern/kern_mbuf.c
index 1ea8e9d..5e634d7 100644
--- a/sys/kern/kern_mbuf.c
+++ b/sys/kern/kern_mbuf.c
@@ -424,6 +424,7 @@ mb_ctor_mbuf(void *mem, int size, void *arg, int how)
 
 	m = (struct mbuf *)mem;
 	flags = args->flags;
+	MPASS((flags & M_NOFREE) == 0);
 
 	error = m_init(m, how, type, flags);
 
@@ -572,6 +573,7 @@ mb_ctor_pack(void *mem, int size, void *arg, int how)
 	args = (struct mb_args *)arg;
 	flags = args->flags;
 	type = args->type;
+	MPASS((flags & M_NOFREE) == 0);
 
 #ifdef INVARIANTS
 	trash_ctor(m->m_ext.ext_buf, MCLBYTES, arg, how);
diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index baadc21..62dfda6 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -1670,7 +1670,7 @@ m_unshare(struct mbuf *m0, int how)
 		 * don't know how to break up the non-contiguous memory when
 		 * doing DMA.
 		 */
-		n = m_getcl(how, m->m_type, m->m_flags);
+		n = m_getcl(how, m->m_type, m->m_flags & M_COPYFLAGS);
 		if (n == NULL) {
 			m_freem(m0);
 			return (NULL);
@@ -1700,7 +1700,7 @@ m_unshare(struct mbuf *m0, int how)
 				break;
 			off += cc;
 
-			n = m_getcl(how, m->m_type, m->m_flags);
+			n = m_getcl(how, m->m_type, m->m_flags & M_COPYFLAGS);
 			if (n == NULL) {
 				m_freem(mfirst);
 				m_freem(m0);