linux-kernel - [PATCH net] ipv4: ping: fix bind address validity check

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Message-Id: <20220617020213.1881452-1-cmllamas@google.com>
Date:   Fri, 17 Jun 2022 02:02:13 +0000
From:   Carlos Llamas <cmllamas@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Riccardo Paolo Bestetti <pbl@...tov.io>
Cc:     kernel-team@...roid.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, Carlos Llamas <cmllamas@...gle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        "Maciej Żenczykowski" <maze@...gle.com>
Subject: [PATCH net] ipv4: ping: fix bind address validity check

Commit 8ff978b8b222 ("ipv4/raw: support binding to nonlocal addresses")
introduced a helper function to fold duplicated validity checks of bind
addresses into inet_addr_valid_or_nonlocal(). However, this caused an
unintended regression in ping_check_bind_addr(), which previously would
reject binding to multicast and broadcast addresses, but now these are
both incorrectly allowed as reported in [1].

This patch restores the original check. A simple reordering is done to
improve readability and make it evident that multicast and broadcast
addresses should not be allowed. Also, add an early exit for INADDR_ANY
which replaces lost behavior added by commit 0ce779a9f501 ("net: Avoid
unnecessary inet_addr_type() call when addr is INADDR_ANY").

[1] https://lore.kernel.org/netdev/CANP3RGdkAcDyAZoT1h8Gtuu0saq+eOrrTiWbxnOs+5zn+cpyKg@mail.gmail.com/

Fixes: 8ff978b8b222 ("ipv4/raw: support binding to nonlocal addresses")
Cc: Miaohe Lin <linmiaohe@...wei.com>
Cc: Riccardo Paolo Bestetti <pbl@...tov.io>
Reported-by: Maciej Żenczykowski <maze@...gle.com>
Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
---
 net/ipv4/ping.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index 1a43ca73f94d..3c6101def7d6 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -319,12 +319,16 @@ static int ping_check_bind_addr(struct sock *sk, struct inet_sock *isk,
 		pr_debug("ping_check_bind_addr(sk=%p,addr=%pI4,port=%d)\n",
 			 sk, &addr->sin_addr.s_addr, ntohs(addr->sin_port));
 
+		if (addr->sin_addr.s_addr == htonl(INADDR_ANY))
+			return 0;
+
 		tb_id = l3mdev_fib_table_by_index(net, sk->sk_bound_dev_if) ? : tb_id;
 		chk_addr_ret = inet_addr_type_table(net, addr->sin_addr.s_addr, tb_id);
 
-		if (!inet_addr_valid_or_nonlocal(net, inet_sk(sk),
-					         addr->sin_addr.s_addr,
-	                                         chk_addr_ret))
+		if (chk_addr_ret == RTN_MULTICAST ||
+		    chk_addr_ret == RTN_BROADCAST ||
+		    (chk_addr_ret != RTN_LOCAL &&
+		     !inet_can_nonlocal_bind(net, isk)))
 			return -EADDRNOTAVAIL;
 
 #if IS_ENABLED(CONFIG_IPV6)
-- 
2.36.1.476.g0c4daa206d-goog