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net: mctp: Don't access ifa_index when missing

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[ Upstream commit f11cf946c0a92c560a890d68e4775723353599e1 ]

In mctp_dump_addrinfo, ifa_index can be used to filter interfaces, but
only when the struct ifaddrmsg is provided. Otherwise it will be
comparing to uninitialised memory - reproducible in the syzkaller case from
dhcpd, or busybox "ip addr show".

The kernel MCTP implementation has always filtered by ifa_index, so
existing userspace programs expecting to dump MCTP addresses must
already be passing a valid ifa_index value (either 0 or a real index).

BUG: KMSAN: uninit-value in mctp_dump_addrinfo+0x208/0xac0 net/mctp/device.c:128
 mctp_dump_addrinfo+0x208/0xac0 net/mctp/device.c:128
 rtnl_dump_all+0x3ec/0x5b0 net/core/rtnetlink.c:4380
 rtnl_dumpit+0xd5/0x2f0 net/core/rtnetlink.c:6824
 netlink_dump+0x97b/0x1690 net/netlink/af_netlink.c:2309

Fixes: 583be982d9 ("mctp: Add device handling and netlink interface")
Reported-by: syzbot+e76d52dadc089b9d197f@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68135815.050a0220.3a872c.000e.GAE@google.com/
Reported-by: syzbot+1065a199625a388fce60@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/681357d6.050a0220.14dd7d.000d.GAE@google.com/
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Link: https://patch.msgid.link/20250508-mctp-addr-dump-v2-1-c8a53fd2dd66@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Matt Johnston
2025-05-08 13:18:32 +08:00
committed by Greg Kroah-Hartman
parent 2d45eeb7d5
commit acab78ae12
1 changed files with 11 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
net/mctp/device.c
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@@ -117,11 +117,18 @@ static int mctp_dump_addrinfo(struct sk_buff *skb, struct netlink_callback *cb)
struct net_device *dev;
struct ifaddrmsg *hdr;
struct mctp_dev *mdev;
int ifindex, rc;
int ifindex = 0, rc;
hdr = nlmsg_data(cb->nlh);
// filter by ifindex if requested
ifindex = hdr->ifa_index;
/* Filter by ifindex if a header is provided */
if (cb->nlh->nlmsg_len >= nlmsg_msg_size(sizeof(*hdr))) {
hdr = nlmsg_data(cb->nlh);
ifindex = hdr->ifa_index;
} else {
if (cb->strict_check) {
NL_SET_ERR_MSG(cb->extack, "mctp: Invalid header for addr dump request");
return -EINVAL;
}
}
rcu_read_lock();
for_each_netdev_dump(net, dev, mcb->ifindex) {