[PATCH net-next v2] net: validate SO_TXTIME clockid coming from userspace

[Abhishek Chauhan]

Currently there are no strict checks while setting SO_TXTIME
from userspace. With the recent development in skb->tstamp_type
clockid with unsupported clocks results in warn_on_once, which causes
unnecessary aborts in some systems which enables panic on warns.

Add validation in setsockopt to support only CLOCK_REALTIME,
CLOCK_MONOTONIC and CLOCK_TAI to be set from userspace.

Link: https://lore.kernel.org/netdev/bc037db4-58bb-4861-ac31-a361a93841d3@xxxxxxxxx/
Link: https://lore.kernel.org/lkml/6bdba7b6-fd22-4ea5-a356-12268674def1@xxxxxxxxxxx/
Fixes: 1693c5db6ab8 ("net: Add additional bit to support clockid_t timestamp type")
Reported-by: syzbot+d7b227731ec589e7f4f0@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=d7b227731ec589e7f4f0
Reported-by: syzbot+30a35a2e9c5067cc43fa@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=30a35a2e9c5067cc43fa
Signed-off-by: Abhishek Chauhan <quic_abchauha@xxxxxxxxxxx>
Acked-by: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
---
Changes since v1 
- Moved from net to net-next since 
  Fixes tag is available only on net-next
  as mentioned by Martin 
- Added direct link to design discussion as 
  mentioned by Willem.
- Parameter in the sockopt_validate_clockid
  is of type __kernel_clockid_t so changed it from 
  int to __kernel_clockid_t as mentioned by 
  Willem.
- Added Acked-by tag. 

 net/core/sock.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/net/core/sock.c b/net/core/sock.c
index 8629f9aecf91..d497285f283a 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1083,6 +1083,17 @@ bool sockopt_capable(int cap)
 }
 EXPORT_SYMBOL(sockopt_capable);
 
+static int sockopt_validate_clockid(__kernel_clockid_t value)
+{
+	switch (value) {
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_TAI:
+		return 0;
+	}
+	return -EINVAL;
+}
+
 /*
  *	This is meant for all protocols to use and covers goings on
  *	at the socket level. Everything here is generic.
@@ -1497,6 +1508,11 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
 			ret = -EPERM;
 			break;
 		}
+
+		ret = sockopt_validate_clockid(sk_txtime.clockid);
+		if (ret)
+			break;
+
 		sock_valbool_flag(sk, SOCK_TXTIME, true);
 		sk->sk_clockid = sk_txtime.clockid;
 		sk->sk_txtime_deadline_mode =
-- 
2.25.1