net/rose: prevent integer overflows in rose_setsockopt()

In case of possible unpredictably large arguments passed to
rose_setsockopt() and multiplied by extra values on top of that,
integer overflows may occur.

Do the safest minimum and fix these issues by checking the
contents of 'opt' and returning -EINVAL if they are too large. Also,
switch to unsigned int and remove useless check for negative 'opt'
in ROSE_IDLE case.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Link: https://patch.msgid.link/20250115164220.19954-1-n.zhandarovich@fintech.ru
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Nikita Zhandarovich

net/rose/af_rose.c

@@ -397,15 +397,15 @@ static int rose_setsockopt(struct socket *sock, int level, int optname,
 {
 	struct sock *sk = sock->sk;
 	struct rose_sock *rose = rose_sk(sk);
-	int opt;
+	unsigned int opt;
 
 	if (level != SOL_ROSE)
 		return -ENOPROTOOPT;
 
-	if (optlen < sizeof(int))
+	if (optlen < sizeof(unsigned int))
 		return -EINVAL;
 
-	if (copy_from_sockptr(&opt, optval, sizeof(int)))
+	if (copy_from_sockptr(&opt, optval, sizeof(unsigned int)))
 		return -EFAULT;
 
 	switch (optname) {
@@ -414,31 +414,31 @@ static int rose_setsockopt(struct socket *sock, int level, int optname,
 		return 0;
 
 	case ROSE_T1:
-		if (opt < 1)
+		if (opt < 1 || opt > UINT_MAX / HZ)
 			return -EINVAL;
 		rose->t1 = opt * HZ;
 		return 0;
 
 	case ROSE_T2:
-		if (opt < 1)
+		if (opt < 1 || opt > UINT_MAX / HZ)
 			return -EINVAL;
 		rose->t2 = opt * HZ;
 		return 0;
 
 	case ROSE_T3:
-		if (opt < 1)
+		if (opt < 1 || opt > UINT_MAX / HZ)
 			return -EINVAL;
 		rose->t3 = opt * HZ;
 		return 0;
 
 	case ROSE_HOLDBACK:
-		if (opt < 1)
+		if (opt < 1 || opt > UINT_MAX / HZ)
 			return -EINVAL;
 		rose->hb = opt * HZ;
 		return 0;
 
 	case ROSE_IDLE:
-		if (opt < 0)
+		if (opt > UINT_MAX / (60 * HZ))
 			return -EINVAL;
 		rose->idle = opt * 60 * HZ;
 		return 0;