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rtnetlink: return ENODEV when ifname does not exist and group is given

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[ Upstream commit ef2a7c9065 ]

When the interface does not exist, and a group is given, the given
parameters are being set to all interfaces of the given group. The given
IFNAME/ALT_IF_NAME are being ignored in that case.

That can be dangerous since a typo (or a deleted interface) can produce
weird side effects for caller:

Case 1:

 IFLA_IFNAME=valid_interface
 IFLA_GROUP=1
 MTU=1234

Case 1 will update MTU and group of the given interface "valid_interface".

Case 2:

 IFLA_IFNAME=doesnotexist
 IFLA_GROUP=1
 MTU=1234

Case 2 will update MTU of all interfaces in group 1. IFLA_IFNAME is
ignored in this case

This behaviour is not consistent and dangerous. In order to fix this issue,
we now return ENODEV when the given IFNAME does not exist.

Signed-off-by: Florent Fourcot <florent.fourcot@wifirst.fr>
Signed-off-by: Brian Baboch <brian.baboch@wifirst.fr>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Stable-dep-of: 30188bd783 ("rtnetlink: Reject negative ifindexes in RTM_NEWLINK")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Florent Fourcot 2022-04-15 18:53:27 +02:00 • committed by Justin Hammond
parent c52739c22c
commit 109f1fe215
1 changed files with 14 additions and 4 deletions
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18
net/core/rtnetlink.c
View file

@ -3294,6 +3294,7 @@ static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
struct ifinfomsg *ifm;
char ifname[IFNAMSIZ];
struct nlattr **data;
bool link_specified;
int err;
#ifdef CONFIG_MODULES
@ -3314,12 +3315,16 @@ replay:
ifname[0] = '\0';
ifm = nlmsg_data(nlh);
if (ifm->ifi_index > 0)
if (ifm->ifi_index > 0) {
link_specified = true;
dev = __dev_get_by_index(net, ifm->ifi_index);
else if (tb[IFLA_IFNAME] || tb[IFLA_ALT_IFNAME])
} else if (tb[IFLA_IFNAME] || tb[IFLA_ALT_IFNAME]) {
link_specified = true;
dev = rtnl_dev_get(net, NULL, tb[IFLA_ALT_IFNAME], ifname);
else
} else {
link_specified = false;
dev = NULL;
}
master_dev = NULL;
m_ops = NULL;
@ -3422,7 +3427,12 @@ replay:
}
if (!(nlh->nlmsg_flags & NLM_F_CREATE)) {
if (ifm->ifi_index == 0 && tb[IFLA_GROUP])
/* No dev found and NLM_F_CREATE not set. Requested dev does not exist,
* or it's for a group
*/
if (link_specified)
return -ENODEV;
if (tb[IFLA_GROUP])
return rtnl_group_changelink(skb, net,
nla_get_u32(tb[IFLA_GROUP]),
ifm, extack, tb);