[PATCH AUTOSEL 6.8 08/30] af_packet: avoid a false positive warning in packet_setsockopt()

Sasha Levin
2024-05-27T14:14:33Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 86d43e2bf93ccac88ef71cee36a23282ebd9e427 ]

Although the code is correct, the following line

copy_from_sockptr(&req_u.req, optval, len));

triggers this warning :

memcpy: detected field-spanning write (size 28) of single field "dst" at include/linux/sockptr.h:49 (size 16)

Refactor the code to be more explicit.

Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/packet/af_packet.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index e6a8701a38dbe..59ca1e321db16 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3800,28 +3800,30 @@ packet_setsockopt(struct socket *sock, int level, int optname, sockptr_t optval,
case PACKET_TX_RING:
{
union tpacket_req_u req_u;
- int len;

+ ret = -EINVAL;
lock_sock(sk);
switch (po->tp_version) {
case TPACKET_V1:
case TPACKET_V2:
- len = sizeof(req_u.req);
+ if (optlen < sizeof(req_u.req))
+ break;
+ ret = copy_from_sockptr(&req_u.req, optval,
+ sizeof(req_u.req)) ?
+ -EINVAL : 0;
break;
case TPACKET_V3:
default:
- len = sizeof(req_u.req3);
+ if (optlen < sizeof(req_u.req3))
+ break;
+ ret = copy_from_sockptr(&req_u.req3, optval,
+ sizeof(req_u.req3)) ?
+ -EINVAL : 0;
break;
}
- if (optlen < len) {
- ret = -EINVAL;
- } else {
- if (copy_from_sockptr(&req_u.req, optval, len))
- ret = -EFAULT;
- else
- ret = packet_set_ring(sk, &req_u, 0,
- optname == PACKET_TX_RING);
- }
+ if (!ret)
+ ret = packet_set_ring(sk, &req_u, 0,
+ optname == PACKET_TX_RING);
release_sock(sk);
return ret;
}
--
2.43.0