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Message-ID: <20230421185255.94606-1-kuniyu@amazon.com>
Date: Fri, 21 Apr 2023 11:52:55 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
CC: Patrick McHardy <kaber@...sh.net>,
Pablo Neira Ayuso <pablo@...filter.org>,
Christophe Ricard <christophe-h.ricard@...com>,
Johannes Berg <johannes.berg@...el.com>,
David Ahern <dsahern@...il.com>,
Kuniyuki Iwashima <kuniyu@...zon.com>,
Kuniyuki Iwashima <kuni1840@...il.com>,
<netdev@...r.kernel.org>, Brad Spencer <bspencer@...ckberry.com>
Subject: [PATCH v3 net] netlink: Use copy_to_user() for optval in netlink_getsockopt().
Brad Spencer provided a detailed report [0] that when calling getsockopt()
for AF_NETLINK, some SOL_NETLINK options set only 1 byte even though such
options require at least sizeof(int) as length.
The options return a flag value that fits into 1 byte, but such behaviour
confuses users who do not initialise the variable before calling
getsockopt() and do not strictly check the returned value as char.
Currently, netlink_getsockopt() uses put_user() to copy data to optlen and
optval, but put_user() casts the data based on the pointer, char *optval.
As a result, only 1 byte is set to optval.
To avoid this behaviour, we need to use copy_to_user() or cast optval for
put_user().
Note that this changes the behaviour on big-endian systems, but we document
that the size of optval is int in the man page.
$ man 7 netlink
...
Socket options
To set or get a netlink socket option, call getsockopt(2) to read
or setsockopt(2) to write the option with the option level argument
set to SOL_NETLINK. Unless otherwise noted, optval is a pointer to
an int.
Fixes: 9a4595bc7e67 ("[NETLINK]: Add set/getsockopt options to support more than 32 groups")
Fixes: be0c22a46cfb ("netlink: add NETLINK_BROADCAST_ERROR socket option")
Fixes: 38938bfe3489 ("netlink: add NETLINK_NO_ENOBUFS socket flag")
Fixes: 0a6a3a23ea6e ("netlink: add NETLINK_CAP_ACK socket option")
Fixes: 2d4bc93368f5 ("netlink: extended ACK reporting")
Fixes: 89d35528d17d ("netlink: Add new socket option to enable strict checking on dumps")
Reported-by: Brad Spencer <bspencer@...ckberry.com>
Link: https://lore.kernel.org/netdev/ZD7VkNWFfp22kTDt@datsun.rim.net/
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
v3:
* Keep errno for unknown opts if len < sizeof(int)
* Update changelog
v2: https://lore.kernel.org/netdev/20230420233351.77166-1-kuniyu@amazon.com/
* Keep the len check and setting
* Update changelog
v1: https://lore.kernel.org/netdev/20230419004246.25770-1-kuniyu@amazon.com/
---
net/netlink/af_netlink.c | 75 ++++++++++++----------------------------
1 file changed, 23 insertions(+), 52 deletions(-)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index f365dfdd672d..9b6eb28e6e94 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1742,7 +1742,8 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
{
struct sock *sk = sock->sk;
struct netlink_sock *nlk = nlk_sk(sk);
- int len, val, err;
+ unsigned int flag;
+ int len, val;
if (level != SOL_NETLINK)
return -ENOPROTOOPT;
@@ -1754,39 +1755,17 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
switch (optname) {
case NETLINK_PKTINFO:
- if (len < sizeof(int))
- return -EINVAL;
- len = sizeof(int);
- val = nlk->flags & NETLINK_F_RECV_PKTINFO ? 1 : 0;
- if (put_user(len, optlen) ||
- put_user(val, optval))
- return -EFAULT;
- err = 0;
+ flag = NETLINK_F_RECV_PKTINFO;
break;
case NETLINK_BROADCAST_ERROR:
- if (len < sizeof(int))
- return -EINVAL;
- len = sizeof(int);
- val = nlk->flags & NETLINK_F_BROADCAST_SEND_ERROR ? 1 : 0;
- if (put_user(len, optlen) ||
- put_user(val, optval))
- return -EFAULT;
- err = 0;
+ flag = NETLINK_F_BROADCAST_SEND_ERROR;
break;
case NETLINK_NO_ENOBUFS:
- if (len < sizeof(int))
- return -EINVAL;
- len = sizeof(int);
- val = nlk->flags & NETLINK_F_RECV_NO_ENOBUFS ? 1 : 0;
- if (put_user(len, optlen) ||
- put_user(val, optval))
- return -EFAULT;
- err = 0;
+ flag = NETLINK_F_RECV_NO_ENOBUFS;
break;
case NETLINK_LIST_MEMBERSHIPS: {
- int pos, idx, shift;
+ int pos, idx, shift, err = 0;
- err = 0;
netlink_lock_table();
for (pos = 0; pos * 8 < nlk->ngroups; pos += sizeof(u32)) {
if (len - pos < sizeof(u32))
@@ -1803,40 +1782,32 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
if (put_user(ALIGN(nlk->ngroups / 8, sizeof(u32)), optlen))
err = -EFAULT;
netlink_unlock_table();
- break;
+ return err;
}
case NETLINK_CAP_ACK:
- if (len < sizeof(int))
- return -EINVAL;
- len = sizeof(int);
- val = nlk->flags & NETLINK_F_CAP_ACK ? 1 : 0;
- if (put_user(len, optlen) ||
- put_user(val, optval))
- return -EFAULT;
- err = 0;
+ flag = NETLINK_F_CAP_ACK;
break;
case NETLINK_EXT_ACK:
- if (len < sizeof(int))
- return -EINVAL;
- len = sizeof(int);
- val = nlk->flags & NETLINK_F_EXT_ACK ? 1 : 0;
- if (put_user(len, optlen) || put_user(val, optval))
- return -EFAULT;
- err = 0;
+ flag = NETLINK_F_EXT_ACK;
break;
case NETLINK_GET_STRICT_CHK:
- if (len < sizeof(int))
- return -EINVAL;
- len = sizeof(int);
- val = nlk->flags & NETLINK_F_STRICT_CHK ? 1 : 0;
- if (put_user(len, optlen) || put_user(val, optval))
- return -EFAULT;
- err = 0;
+ flag = NETLINK_F_STRICT_CHK;
break;
default:
- err = -ENOPROTOOPT;
+ return -ENOPROTOOPT;
}
- return err;
+
+ if (len < sizeof(int))
+ return -EINVAL;
+
+ len = sizeof(int);
+ val = nlk->flags & flag ? 1 : 0;
+
+ if (put_user(len, optlen) ||
+ copy_to_user(optval, &val, len))
+ return -EFAULT;
+
+ return 0;
}
static void netlink_cmsg_recv_pktinfo(struct msghdr *msg, struct sk_buff *skb)
--
2.30.2
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