From 89d35528d17d25819a755a2b52931e911baebc66 Mon Sep 17 00:00:00 2001 From: David Ahern Date: Sun, 7 Oct 2018 20:16:27 -0700 Subject: netlink: Add new socket option to enable strict checking on dumps Add a new socket option, NETLINK_DUMP_STRICT_CHK, that userspace can use via setsockopt to request strict checking of headers and attributes on dump requests. To get dump features such as kernel side filtering based on data in the header or attributes appended to the dump request, userspace must call setsockopt() for NETLINK_DUMP_STRICT_CHK and a non-zero value. Since the netlink sock and its flags are private to the af_netlink code, the strict checking flag is passed to dump handlers via a flag in the netlink_callback struct. For old userspace on new kernel there is no impact as all of the data checks in later patches are wrapped in a check on the new strict flag. For new userspace on old kernel, the setsockopt will fail and even if new userspace sets data in the headers and appended attributes the kernel will silently ignore it. Moving forward when the setsockopt succeeds, the new userspace on old kernel means the dump request can pass an attribute the kernel does not understand. The dump will then fail as the older kernel does not understand it. New userspace on new kernel setting the socket option gets the benefit of the improved data dump. Kernel side the NETLINK_DUMP_STRICT_CHK uapi is converted to a generic NETLINK_F_STRICT_CHK flag which can potentially be leveraged for tighter checking on the NEW, DEL, and SET commands. Signed-off-by: David Ahern Acked-by: Christian Brauner Signed-off-by: David S. Miller --- net/netlink/af_netlink.c | 21 ++++++++++++++++++++- net/netlink/af_netlink.h | 1 + 2 files changed, 21 insertions(+), 1 deletion(-) (limited to 'net/netlink') diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 7ac585f33a9e..e613a9f89600 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1706,6 +1706,13 @@ static int netlink_setsockopt(struct socket *sock, int level, int optname, nlk->flags &= ~NETLINK_F_EXT_ACK; err = 0; break; + case NETLINK_DUMP_STRICT_CHK: + if (val) + nlk->flags |= NETLINK_F_STRICT_CHK; + else + nlk->flags &= ~NETLINK_F_STRICT_CHK; + err = 0; + break; default: err = -ENOPROTOOPT; } @@ -1799,6 +1806,15 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname, return -EFAULT; err = 0; break; + case NETLINK_DUMP_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; + break; default: err = -ENOPROTOOPT; } @@ -2282,9 +2298,9 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb, const struct nlmsghdr *nlh, struct netlink_dump_control *control) { + struct netlink_sock *nlk, *nlk2; struct netlink_callback *cb; struct sock *sk; - struct netlink_sock *nlk; int ret; refcount_inc(&skb->users); @@ -2318,6 +2334,9 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb, cb->min_dump_alloc = control->min_dump_alloc; cb->skb = skb; + nlk2 = nlk_sk(NETLINK_CB(skb).sk); + cb->strict_check = !!(nlk2->flags & NETLINK_F_STRICT_CHK); + if (control->start) { ret = control->start(cb); if (ret) diff --git a/net/netlink/af_netlink.h b/net/netlink/af_netlink.h index 962de7b3c023..5f454c8de6a4 100644 --- a/net/netlink/af_netlink.h +++ b/net/netlink/af_netlink.h @@ -15,6 +15,7 @@ #define NETLINK_F_LISTEN_ALL_NSID 0x10 #define NETLINK_F_CAP_ACK 0x20 #define NETLINK_F_EXT_ACK 0x40 +#define NETLINK_F_STRICT_CHK 0x80 #define NLGRPSZ(x) (ALIGN(x, sizeof(unsigned long) * 8) / 8) #define NLGRPLONGS(x) (NLGRPSZ(x)/sizeof(unsigned long)) -- cgit v1.2.3