[PATCH AUTOSEL 5.15 15/16] ipv6: raw: check passed optlen before reading

[Sasha Levin <sashal@kernel.org>]

From: Tamir Duberstein <tamird@gmail.com>

[ Upstream commit fb7bc9204095090731430c8921f9e629740c110a ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/ipv6/raw.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 60f1e4f5be5aa..c51d5ce3711c2 100644
--- 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;
 
-- 
2.34.1