Re: [PATCH v4 RESEND net-next] net: socket: use BIT() for MSG_*

From: Menglong Dong <redacted>
Date: Wed, 17 Mar 2021 16:21:14 +0800

Hello,

On Wed, Mar 17, 2021 at 9:38 AM Guenter Roeck [off-list ref] wrote:

quoted

On Wed, Mar 17, 2021 at 01:02:51AM +0200, Andy Shevchenko wrote:

quoted

On Wednesday, March 17, 2021, Guenter Roeck [off-list ref] wrote:

...

quoted

The problem is in net/packet/af_packet.c:packet_recvmsg(). This function,
as well as all other rcvmsg functions, is declared as

static int packet_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
                          int flags)

MSG_CMSG_COMPAT (0x80000000) is set in flags, meaning its value is negative.
This is then evaluated in

       if (flags & ~(MSG_PEEK|MSG_DONTWAIT|MSG_TRUNC|MSG_CMSG_COMPAT|MSG_ERRQUEUE))
                goto out;

So what should I do? Revert this patch? Or fix the usages of 'flags'?

I already reverted this patch from net-next to fix the regression.