The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 158b515f703e75e7d68289bf4d98c664e1d632df Mon Sep 17 00:00:00 2001

From: George Kennedy george.kennedy@oracle.com Date: Thu, 16 Dec 2021 13:25:32 -0500 Subject: [PATCH] tun: avoid double free in tun_free_netdev

Avoid double free in tun_free_netdev() by moving the dev->tstats and tun->security allocs to a new ndo_init routine (tun_net_init()) that will be called by register_netdevice(). ndo_init is paired with the desctructor (tun_free_netdev()), so if there's an error in register_netdevice() the destructor will handle the frees.

BUG: KASAN: double-free or invalid-free in selinux_tun_dev_free_security+0x1a/0x20 security/selinux/hooks.c:5605

CPU: 0 PID: 25750 Comm: syz-executor416 Not tainted 5.16.0-rc2-syzk #1 Hardware name: Red Hat KVM, BIOS Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x89/0xb5 lib/dump_stack.c:106 print_address_description.constprop.9+0x28/0x160 mm/kasan/report.c:247 kasan_report_invalid_free+0x55/0x80 mm/kasan/report.c:372 ____kasan_slab_free mm/kasan/common.c:346 [inline] __kasan_slab_free+0x107/0x120 mm/kasan/common.c:374 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:1723 [inline] slab_free_freelist_hook mm/slub.c:1749 [inline] slab_free mm/slub.c:3513 [inline] kfree+0xac/0x2d0 mm/slub.c:4561 selinux_tun_dev_free_security+0x1a/0x20 security/selinux/hooks.c:5605 security_tun_dev_free_security+0x4f/0x90 security/security.c:2342 tun_free_netdev+0xe6/0x150 drivers/net/tun.c:2215 netdev_run_todo+0x4df/0x840 net/core/dev.c:10627 rtnl_unlock+0x13/0x20 net/core/rtnetlink.c:112 __tun_chr_ioctl+0x80c/0x2870 drivers/net/tun.c:3302 tun_chr_ioctl+0x2f/0x40 drivers/net/tun.c:3311 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x19d/0x220 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported-by: syzkaller syzkaller@googlegroups.com Signed-off-by: George Kennedy george.kennedy@oracle.com Suggested-by: Jakub Kicinski kuba@kernel.org Link: https://lore.kernel.org/r/1639679132-19884-1-git-send-email-george.kennedy@o... Signed-off-by: Jakub Kicinski kuba@kernel.org

diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 1572878c3403..45a67e72a02c 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -209,6 +209,9 @@ struct tun_struct { struct tun_prog __rcu *steering_prog; struct tun_prog __rcu *filter_prog; struct ethtool_link_ksettings link_ksettings; + /* init args */ + struct file *file; + struct ifreq *ifr; };

struct veth { @@ -216,6 +219,9 @@ struct veth { __be16 h_vlan_TCI; };

+static void tun_flow_init(struct tun_struct *tun); +static void tun_flow_uninit(struct tun_struct *tun); + static int tun_napi_receive(struct napi_struct *napi, int budget) { struct tun_file *tfile = container_of(napi, struct tun_file, napi); @@ -953,6 +959,49 @@ static int check_filter(struct tap_filter *filter, const struct sk_buff *skb)

static const struct ethtool_ops tun_ethtool_ops;

+static int tun_net_init(struct net_device *dev) +{ + struct tun_struct *tun = netdev_priv(dev); + struct ifreq *ifr = tun->ifr; + int err; + + dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats); + if (!dev->tstats) + return -ENOMEM; + + spin_lock_init(&tun->lock); + + err = security_tun_dev_alloc_security(&tun->security); + if (err < 0) { + free_percpu(dev->tstats); + return err; + } + + tun_flow_init(tun); + + dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST | + TUN_USER_FEATURES | NETIF_F_HW_VLAN_CTAG_TX | + NETIF_F_HW_VLAN_STAG_TX; + dev->features = dev->hw_features | NETIF_F_LLTX; + dev->vlan_features = dev->features & + ~(NETIF_F_HW_VLAN_CTAG_TX | + NETIF_F_HW_VLAN_STAG_TX); + + tun->flags = (tun->flags & ~TUN_FEATURES) | + (ifr->ifr_flags & TUN_FEATURES); + + INIT_LIST_HEAD(&tun->disabled); + err = tun_attach(tun, tun->file, false, ifr->ifr_flags & IFF_NAPI, + ifr->ifr_flags & IFF_NAPI_FRAGS, false); + if (err < 0) { + tun_flow_uninit(tun); + security_tun_dev_free_security(tun->security); + free_percpu(dev->tstats); + return err; + } + return 0; +} + /* Net device detach from fd. */ static void tun_net_uninit(struct net_device *dev) { @@ -1169,6 +1218,7 @@ static int tun_net_change_carrier(struct net_device *dev, bool new_carrier) }

static const struct net_device_ops tun_netdev_ops = { + .ndo_init = tun_net_init, .ndo_uninit = tun_net_uninit, .ndo_open = tun_net_open, .ndo_stop = tun_net_close, @@ -1252,6 +1302,7 @@ static int tun_xdp_tx(struct net_device *dev, struct xdp_buff *xdp) }

static const struct net_device_ops tap_netdev_ops = { + .ndo_init = tun_net_init, .ndo_uninit = tun_net_uninit, .ndo_open = tun_net_open, .ndo_stop = tun_net_close, @@ -1292,7 +1343,7 @@ static void tun_flow_uninit(struct tun_struct *tun) #define MAX_MTU 65535

/* Initialize net device. */ -static void tun_net_init(struct net_device *dev) +static void tun_net_initialize(struct net_device *dev) { struct tun_struct *tun = netdev_priv(dev);

@@ -2206,11 +2257,6 @@ static void tun_free_netdev(struct net_device *dev) BUG_ON(!(list_empty(&tun->disabled)));

free_percpu(dev->tstats); - /* We clear tstats so that tun_set_iff() can tell if - * tun_free_netdev() has been called from register_netdevice(). - */ - dev->tstats = NULL; - tun_flow_uninit(tun); security_tun_dev_free_security(tun->security); __tun_set_ebpf(tun, &tun->steering_prog, NULL); @@ -2716,41 +2762,16 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) tun->rx_batched = 0; RCU_INIT_POINTER(tun->steering_prog, NULL);

- dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats); - if (!dev->tstats) { - err = -ENOMEM; - goto err_free_dev; - } - - spin_lock_init(&tun->lock); - - err = security_tun_dev_alloc_security(&tun->security); - if (err < 0) - goto err_free_stat; - - tun_net_init(dev); - tun_flow_init(tun); + tun->ifr = ifr; + tun->file = file;

- dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST | - TUN_USER_FEATURES | NETIF_F_HW_VLAN_CTAG_TX | - NETIF_F_HW_VLAN_STAG_TX; - dev->features = dev->hw_features | NETIF_F_LLTX; - dev->vlan_features = dev->features & - ~(NETIF_F_HW_VLAN_CTAG_TX | - NETIF_F_HW_VLAN_STAG_TX); - - tun->flags = (tun->flags & ~TUN_FEATURES) | - (ifr->ifr_flags & TUN_FEATURES); - - INIT_LIST_HEAD(&tun->disabled); - err = tun_attach(tun, file, false, ifr->ifr_flags & IFF_NAPI, - ifr->ifr_flags & IFF_NAPI_FRAGS, false); - if (err < 0) - goto err_free_flow; + tun_net_initialize(dev);

err = register_netdevice(tun->dev); - if (err < 0) - goto err_detach; + if (err < 0) { + free_netdev(dev); + return err; + } /* free_netdev() won't check refcnt, to avoid race * with dev_put() we need publish tun after registration. */ @@ -2767,24 +2788,6 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)

strcpy(ifr->ifr_name, tun->dev->name); return 0; - -err_detach: - tun_detach_all(dev); - /* We are here because register_netdevice() has failed. - * If register_netdevice() already called tun_free_netdev() - * while dealing with the error, dev->stats has been cleared. - */ - if (!dev->tstats) - goto err_free_dev; - -err_free_flow: - tun_flow_uninit(tun); - security_tun_dev_free_security(tun->security); -err_free_stat: - free_percpu(dev->tstats); -err_free_dev: - free_netdev(dev); - return err; }

static void tun_get_iff(struct tun_struct *tun, struct ifreq *ifr)