ipv6: raw: check passed optlen before reading

Add a check that the user-provided option is at least as long as the
number of bytes we intend to read. Before this patch we would blindly
read sizeof(int) bytes even in cases where the user passed
optlen<sizeof(int), which would potentially read garbage or fault.

Discovered by new tests in https://github.com/google/gvisor/pull/6957 .

The original get_user call predates history in the git repo.

Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20211229200947.2862255-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 60f1e4f5be5aaeded68aa44b22f6507c7ccdbc01..c51d5ce3711c2e61e9ea2c1b22cb5ec4ee95ae7b 100644 (file)
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -1020,6 +1020,9 @@ static int do_rawv6_setsockopt(struct sock *sk, int level, int optname,
        struct raw6_sock *rp = raw6_sk(sk);
        int val;
 
+       if (optlen < sizeof(val))
+               return -EINVAL;
+
        if (copy_from_sockptr(&val, optval, sizeof(val)))
                return -EFAULT;