From 9384eacd80f3da8d05fd17073eafd1f7fef80b26 Mon Sep 17 00:00:00 2001 From: Nikolay Aleksandrov Date: Thu, 5 Aug 2021 11:29:03 +0300 Subject: [PATCH] net: core: don't call SIOCBRADD/DELIF for non-bridge devices Commit ad2f99aedf8f ("net: bridge: move bridge ioctls out of .ndo_do_ioctl") changed SIOCBRADD/DELIF to use bridge's ioctl hook (br_ioctl_hook) without checking if the target netdevice is actually a bridge which can cause crashes and generally interpreting other devices' private pointers as net_bridge pointers. Crash example (lo - loopback): $ brctl addif lo ens16 BUG: kernel NULL pointer dereference, address: 000000000000059898 #PF: supervisor read access in kernel modede #PF: error_code(0x0000) - not-present pagege PGD 0 P4D 0 ^Ac Oops: 0000 [#1] SMP NOPTI CPU: 2 PID: 1376 Comm: brctl Kdump: loaded Tainted: G W 5.14.0-rc3+ #405 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014 RIP: 0010:add_del_if+0x1f/0x7c [bridge] Code: 80 bf 1b a0 41 5c e9 c0 3c 03 e1 0f 1f 44 00 00 41 55 41 54 41 89 f4 be 0c 00 00 00 55 48 89 fd 53 48 8b 87 88 00 00 00 89 d3 <4c> 8b a8 98 05 00 00 49 8b bd d0 00 00 00 e8 17 d7 f3 e0 84 c0 74 RSP: 0018:ffff888109d97cb0 EFLAGS: 00010202^Ac RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 000000000000000c RDI: ffff888101239bc0 RBP: ffff888101239bc0 R08: 0000000000000001 R09: 0000000000000000 R10: ffff888109d97cd8 R11: 00000000000000a3 R12: 0000000000000012 R13: 0000000000000000 R14: ffff888101239bc0 R15: ffff888109d97e10 FS: 00007fc1e365b540(0000) GS:ffff88822be80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000598 CR3: 0000000106506000 CR4: 00000000000006e0 Call Trace: br_ioctl_stub+0x7c/0x441 [bridge] br_ioctl_call+0x6d/0x8a dev_ifsioc+0x325/0x4e8 dev_ioctl+0x46b/0x4e1 sock_do_ioctl+0x7b/0xad sock_ioctl+0x2de/0x2f2 vfs_ioctl+0x1e/0x2b __do_sys_ioctl+0x63/0x86 do_syscall_64+0xcb/0xf2 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7fc1e3589427 Code: 00 00 90 48 8b 05 69 aa 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 39 aa 0c 00 f7 d8 64 89 01 48 RSP: 002b:00007ffc8d501d38 EFLAGS: 00000202 ORIG_RAX: 000000000000001010 RAX: ffffffffffffffda RBX: 0000000000000012 RCX: 00007fc1e3589427 RDX: 00007ffc8d501d60 RSI: 00000000000089a3 RDI: 0000000000000003 RBP: 00007ffc8d501d60 R08: 0000000000000000 R09: fefefeff77686d74 R10: fffffffffffff8f9 R11: 0000000000000202 R12: 00007ffc8d502e06 R13: 00007ffc8d502e06 R14: 0000000000000000 R15: 0000000000000000 Modules linked in: bridge stp llc bonding ipv6 virtio_net [last unloaded: llc]^Ac CR2: 0000000000000598 Reported-by: syzbot+79f4a8692e267bdb7227@syzkaller.appspotmail.com Fixes: ad2f99aedf8f ("net: bridge: move bridge ioctls out of .ndo_do_ioctl") Signed-off-by: Nikolay Aleksandrov Signed-off-by: David S. Miller --- net/core/dev_ioctl.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c index ff16326..0e87237 100644 --- a/net/core/dev_ioctl.c +++ b/net/core/dev_ioctl.c @@ -379,6 +379,8 @@ static int dev_ifsioc(struct net *net, struct ifreq *ifr, void __user *data, case SIOCBRDELIF: if (!netif_device_present(dev)) return -ENODEV; + if (!netif_is_bridge_master(dev)) + return -EOPNOTSUPP; dev_hold(dev); rtnl_unlock(); err = br_ioctl_call(net, netdev_priv(dev), cmd, ifr, NULL); -- 2.7.4