From: John Fastabend <john.fastabend@gmail.com>
Date: Sat, 30 Jun 2018 06:17:41 -0700
Subject: bpf: sockmap, fix smap_list_map_remove when psock is in many maps
Patch-mainline: v4.18-rc4
Git-commit: 54fedb42c6537dcb0102e4a58a88456a6286999d
References: bsc#1109837

If a hashmap is free'd with open socks it removes the reference to
the hash entry from the psock. If that is the last reference to the
psock then it will also be free'd by the reference counting logic.
However the current logic that removes the hash reference from the
list of references is broken. In smap_list_remove() we first check
if the sockmap entry matches and then check if the hashmap entry
matches. But, the sockmap entry sill always match because its NULL in
this case which causes the first entry to be removed from the list.
If this is always the "right" entry (because the user adds/removes
entries in order) then everything is OK but otherwise a subsequent
bpf_tcp_close() may reference a free'd object.

To fix this create two list handlers one for sockmap and one for
sockhash.

Reported-by: syzbot+0ce137753c78f7b6acc1@syzkaller.appspotmail.com
Fixes: 81110384441a ("bpf: sockmap, add hash map support")
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 kernel/bpf/sockmap.c |   34 ++++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 12 deletions(-)

--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -1602,17 +1602,27 @@ free_stab:
 	return ERR_PTR(err);
 }
 
-static void smap_list_remove(struct smap_psock *psock,
-			     struct sock **entry,
-			     struct htab_elem *hash_link)
+static void smap_list_map_remove(struct smap_psock *psock,
+				 struct sock **entry)
 {
 	struct smap_psock_map_entry *e, *tmp;
 
 	list_for_each_entry_safe(e, tmp, &psock->maps, list) {
-		if (e->entry == entry || e->hash_link == hash_link) {
+		if (e->entry == entry)
+			list_del(&e->list);
+	}
+}
+
+static void smap_list_hash_remove(struct smap_psock *psock,
+				  struct htab_elem *hash_link)
+{
+	struct smap_psock_map_entry *e, *tmp;
+
+	list_for_each_entry_safe(e, tmp, &psock->maps, list) {
+		struct htab_elem *c = e->hash_link;
+
+		if (c == hash_link)
 			list_del(&e->list);
-			break;
-		}
 	}
 }
 
@@ -1647,7 +1657,7 @@ static void sock_map_free(struct bpf_map
 		 * to be null and queued for garbage collection.
 		 */
 		if (likely(psock)) {
-			smap_list_remove(psock, &stab->sock_map[i], NULL);
+			smap_list_map_remove(psock, &stab->sock_map[i]);
 			smap_release_sock(psock, sock);
 		}
 		write_unlock_bh(&sock->sk_callback_lock);
@@ -1706,7 +1716,7 @@ static int sock_map_delete_elem(struct b
 
 	if (psock->bpf_parse)
 		smap_stop_sock(psock, sock);
-	smap_list_remove(psock, &stab->sock_map[k], NULL);
+	smap_list_map_remove(psock, &stab->sock_map[k]);
 	smap_release_sock(psock, sock);
 out:
 	write_unlock_bh(&sock->sk_callback_lock);
@@ -1908,7 +1918,7 @@ static int sock_map_ctx_update_elem(stru
 		struct smap_psock *opsock = smap_psock_sk(osock);
 
 		write_lock_bh(&osock->sk_callback_lock);
-		smap_list_remove(opsock, &stab->sock_map[i], NULL);
+		smap_list_map_remove(opsock, &stab->sock_map[i]);
 		smap_release_sock(opsock, osock);
 		write_unlock_bh(&osock->sk_callback_lock);
 	}
@@ -2124,7 +2134,7 @@ static void sock_hash_free(struct bpf_ma
 			 * (psock) to be null and queued for garbage collection.
 			 */
 			if (likely(psock)) {
-				smap_list_remove(psock, NULL, l);
+				smap_list_hash_remove(psock, l);
 				smap_release_sock(psock, sock);
 			}
 			write_unlock_bh(&sock->sk_callback_lock);
@@ -2304,7 +2314,7 @@ static int sock_hash_ctx_update_elem(str
 		psock = smap_psock_sk(l_old->sk);
 
 		hlist_del_rcu(&l_old->hash_node);
-		smap_list_remove(psock, NULL, l_old);
+		smap_list_hash_remove(psock, l_old);
 		smap_release_sock(psock, l_old->sk);
 		free_htab_elem(htab, l_old);
 	}
@@ -2372,7 +2382,7 @@ static int sock_hash_delete_elem(struct
 		 * to be null and queued for garbage collection.
 		 */
 		if (likely(psock)) {
-			smap_list_remove(psock, NULL, l);
+			smap_list_hash_remove(psock, l);
 			smap_release_sock(psock, sock);
 		}
 		write_unlock_bh(&sock->sk_callback_lock);