git: 877fa4f2a2d3 - stable/15 - ifnet: Add some sanity checks

The branch stable/15 has been updated by zlei:

URL: https://cgit.FreeBSD.org/src/commit/?id=877fa4f2a2d37dcd9e828d12dc9736c5e83ffd8c

commit 877fa4f2a2d37dcd9e828d12dc9736c5e83ffd8c
Author:     Zhenlei Huang <zlei@FreeBSD.org>
AuthorDate: 2026-04-07 04:33:05 +0000
Commit:     Zhenlei Huang <zlei@FreeBSD.org>
CommitDate: 2026-04-30 09:51:59 +0000

    ifnet: Add some sanity checks
    
    To be more robust since the checking is now performed where the
    interface is referenced.
    
    While here, remove a redundant check from if_vmove_loan().
    
    Reviewed by:    kp, glebius, pouria
    MFC after:      2 weeks
    Differential Revision:  https://reviews.freebsd.org/D55875
    
    (cherry picked from commit 00d96da231d007673a1672452748d8ea4f6788ae)
---
 sys/net/if.c | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/sys/net/if.c b/sys/net/if.c
index aeb264f2ac3f..75ef79738010 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -438,8 +438,12 @@ VNET_SYSINIT(vnet_if_init, SI_SUB_INIT_IF, SI_ORDER_SECOND, vnet_if_init,
 static void
 if_link_ifnet(struct ifnet *ifp)
 {
-
 	IFNET_WLOCK();
+
+	MPASS(refcount_load(&ifp->if_refcount) > 0);
+	MPASS(ifp->if_vnet == curvnet);
+	MPASS(ifindex_table[ifp->if_index].ife_ifnet == ifp);
+
 	CK_STAILQ_INSERT_TAIL(&V_ifnet, ifp, if_link);
 #ifdef VIMAGE
 	curvnet->vnet_ifcnt++;
@@ -456,6 +460,10 @@ if_unlink_ifnet(struct ifnet *ifp, bool vmove)
 	IFNET_WLOCK();
 	CK_STAILQ_FOREACH(iter, &V_ifnet, if_link)
 		if (iter == ifp) {
+			MPASS(refcount_load(&ifp->if_refcount) > 0);
+			MPASS(ifp->if_vnet == curvnet);
+			MPASS(ifindex_table[ifp->if_index].ife_ifnet == ifp);
+
 			CK_STAILQ_REMOVE(&V_ifnet, ifp, ifnet, if_link);
 #ifdef VIMAGE
 			curvnet->vnet_ifcnt--;
@@ -1298,8 +1306,6 @@ if_vmove_loan(struct thread *td, struct ifnet *ifp, char *ifname, int jid)
 	struct ifnet *difp;
 	bool found;
 
-	MPASS(ifindex_table[ifp->if_index].ife_ifnet == ifp);
-
 	/* Try to find the prison within our visibility. */
 	sx_slock(&allprison_lock);
 	pr = prison_find_child(td->td_ucred->cr_prison, jid);
@@ -2222,14 +2228,13 @@ ifunit_ref(const char *name)
 	NET_EPOCH_ENTER(et);
 	CK_STAILQ_FOREACH(ifp, &V_ifnet, if_link) {
 		if (strncmp(name, ifp->if_xname, IFNAMSIZ) == 0 &&
-		    !(ifp->if_flags & IFF_DYING))
+		    !(ifp->if_flags & IFF_DYING)) {
+			MPASS(ifp->if_vnet == curvnet);
+			MPASS(ifindex_table[ifp->if_index].ife_ifnet == ifp);
+			if_ref(ifp);
 			break;
+		}
 	}
-	if (ifp != NULL) {
-		if_ref(ifp);
-		MPASS(ifindex_table[ifp->if_index].ife_ifnet == ifp);
-	}
-
 	NET_EPOCH_EXIT(et);
 	return (ifp);
 }
@@ -2242,8 +2247,12 @@ ifunit(const char *name)
 
 	NET_EPOCH_ENTER(et);
 	CK_STAILQ_FOREACH(ifp, &V_ifnet, if_link) {
-		if (strncmp(name, ifp->if_xname, IFNAMSIZ) == 0)
+		if (strncmp(name, ifp->if_xname, IFNAMSIZ) == 0) {
+			MPASS(refcount_load(&ifp->if_refcount) > 0);
+			MPASS(ifp->if_vnet == curvnet);
+			MPASS(ifindex_table[ifp->if_index].ife_ifnet == ifp);
 			break;
+		}
 	}
 	NET_EPOCH_EXIT(et);
 	return (ifp);