From: Kuniyuki Iwashima kuniyu@amazon.com
[ 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: 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@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 --- 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 011ec7d9a719e..84a7a29be49d8 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1752,7 +1752,8 @@ 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; @@ -1764,39 +1765,17 @@ 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)) @@ -1813,40 +1792,32 @@ 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)