net: compat: Update get_compat_msghdr() to match copy_msghdr_from_user() behaviour

[ Upstream commit 91edd096e224941131f896b86838b1e59553696a ]

Commit db31c55a6fb2 (net: clamp ->msg_namelen instead of returning an
error) introduced the clamping of msg_namelen when the unsigned value
was larger than sizeof(struct sockaddr_storage). This caused a
msg_namelen of -1 to be valid. The native code was subsequently fixed by
commit dbb490b96584 (net: socket: error on a negative msg_namelen).

In addition, the native code sets msg_namelen to 0 when msg_name is
NULL. This was done in commit (6a2a2b3ae075 net:socket: set msg_namelen
to 0 if msg_name is passed as NULL in msghdr struct from userland) and
subsequently updated by 08adb7dabd48 (fold verify_iovec() into
copy_msghdr_from_user()).

This patch brings the get_compat_msghdr() in line with
copy_msghdr_from_user().

Fixes: db31c55a6fb2 (net: clamp ->msg_namelen instead of returning an error)
Cc: David S. Miller <davem@davemloft.net>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/compat.c b/net/compat.c
index 275af79c131bf62cbfee3c63dd2143983497c241..d12529050b291e9951cc03881d46b723f98363d0 100644 (file)
--- a/net/compat.c
+++ b/net/compat.c
@@ -71,6 +71,13 @@ int get_compat_msghdr(struct msghdr *kmsg, struct compat_msghdr __user *umsg)
            __get_user(kmsg->msg_controllen, &umsg->msg_controllen) ||
            __get_user(kmsg->msg_flags, &umsg->msg_flags))
                return -EFAULT;
+
+       if (!tmp1)
+               kmsg->msg_namelen = 0;
+
+       if (kmsg->msg_namelen < 0)
+               return -EINVAL;
+
        if (kmsg->msg_namelen > sizeof(struct sockaddr_storage))
                kmsg->msg_namelen = sizeof(struct sockaddr_storage);
        kmsg->msg_name = compat_ptr(tmp1);