netdev - [bpf PATCH v2 1/2] bpf: sockmap update rollback on error can incorrectly dec prog refcnt

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180517210635.13283.94472.stgit@john-Precision-Tower-5810>
Date:   Thu, 17 May 2018 14:06:35 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     ast@...nel.org, daniel@...earbox.net
Cc:     netdev@...r.kernel.org
Subject: [bpf PATCH v2 1/2] bpf: sockmap update rollback on error can
 incorrectly dec prog refcnt

If the user were to only attach one of the parse or verdict programs
then it is possible a subsequent sockmap update could incorrectly
decrement the refcnt on the program. This happens because in the
rollback logic, after an error, we have to decrement the program
reference count when its been incremented. However, we only increment
the program reference count if the user has both a verdict and a
parse program. The reason for this is because, at least at the
moment, both are required for any one to be meaningful. The problem
fixed here is in the rollback path we decrement the program refcnt
even if only one existing. But we never incremented the refcnt in
the first place creating an imbalance.

This patch fixes the error path to handle this case.

Fixes: 2f857d04601a ("bpf: sockmap, remove STRPARSER map_flags and add multi-map support")
Reported-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: John Fastabend <john.fastabend@...il.com>
Acked-by: Martin KaFai Lau <kafai@...com>
---
 kernel/bpf/sockmap.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 098eca5..f03aaa8 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -1717,10 +1717,10 @@ static int sock_map_ctx_update_elem(struct bpf_sock_ops_kern *skops,
 	if (tx_msg) {
 		tx_msg = bpf_prog_inc_not_zero(stab->bpf_tx_msg);
 		if (IS_ERR(tx_msg)) {
-			if (verdict)
-				bpf_prog_put(verdict);
-			if (parse)
+			if (parse && verdict) {
 				bpf_prog_put(parse);
+				bpf_prog_put(verdict);
+			}
 			return PTR_ERR(tx_msg);
 		}
 	}
@@ -1805,10 +1805,10 @@ static int sock_map_ctx_update_elem(struct bpf_sock_ops_kern *skops,
 out_free:
 	smap_release_sock(psock, sock);
 out_progs:
-	if (verdict)
-		bpf_prog_put(verdict);
-	if (parse)
+	if (parse && verdict) {
 		bpf_prog_put(parse);
+		bpf_prog_put(verdict);
+	}
 	if (tx_msg)
 		bpf_prog_put(tx_msg);
 	write_unlock_bh(&sock->sk_callback_lock);