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netlink: Use copy_to_user() for optval in netlink_getsockopt().

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[ Upstream commit d913d32cc2707e9cd24fe6fa6d7d470e9c728980 ]

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: 9a4595bc7e ("[NETLINK]: Add set/getsockopt options to support more than 32 groups")
Fixes: be0c22a46c ("netlink: add NETLINK_BROADCAST_ERROR socket option")
Fixes: 38938bfe34 ("netlink: add NETLINK_NO_ENOBUFS socket flag")
Fixes: 0a6a3a23ea ("netlink: add NETLINK_CAP_ACK socket option")
Fixes: 2d4bc93368 ("netlink: extended ACK reporting")
Fixes: 89d35528d1 ("netlink: Add new socket option to enable strict checking on dumps")
Reported-by: Brad Spencer <bspencer@blackberry.com>
Link: https://lore.kernel.org/netdev/ZD7VkNWFfp22kTDt@datsun.rim.net/
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Link: https://lore.kernel.org/r/20230421185255.94606-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kuniyuki Iwashima 2023-04-21 11:52:55 -07:00 committed by Greg Kroah-Hartman
parent 952030c914
commit f040bee291
1 changed files with 23 additions and 52 deletions
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75
net/netlink/af_netlink.c
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@ -1731,7 +1731,8 @@ 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;
@ -1743,39 +1744,17 @@ 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))
@ -1792,40 +1771,32 @@ 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)