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Date: Sun, 9 May 2021 16:11:11 -0600 From: David Ahern <dsahern@...il.com> To: Florian Westphal <fw@...len.de>, netdev@...r.kernel.org Subject: Re: [PATCH iproute2] mptcp: avoid uninitialised errno usage On 5/3/21 4:36 AM, Florian Westphal wrote: > The function called *might* set errno based on errno value in NLMSG_ERROR > message, but in case no such message exists errno is left alone. > > This may cause ip to fail with > "can't subscribe to mptcp events: Success" > > on kernels that support mptcp but lack event support (all kernels <= 5.11). > > Set errno to a meaningful value. This will then still exit with the > more specific 'permission denied' or some such when called by process > that lacks CAP_NET_ADMIN on 5.12 and later. > > Fixes: ff619e4fd370 ("mptcp: add support for event monitoring") > Signed-off-by: Florian Westphal <fw@...len.de> > --- > ip/ipmptcp.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/ip/ipmptcp.c b/ip/ipmptcp.c > index 5f490f0026d9..504b5b2f5329 100644 > --- a/ip/ipmptcp.c > +++ b/ip/ipmptcp.c > @@ -491,6 +491,9 @@ out: > > static int mptcp_monitor(void) > { > + /* genl_add_mcast_grp may or may not set errno */ > + errno = EOPNOTSUPP; > + > if (genl_add_mcast_grp(&genl_rth, genl_family, MPTCP_PM_EV_GRP_NAME) < 0) { > perror("can't subscribe to mptcp events"); > return 1; > Seems like this should be set in genl_add_mcast_grp vs its caller.
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