From: Yang Yingliang yangyingliang@huawei.com
[ Upstream commit 77f22f92dff8e7b45c7786a430626d38071d4670 ]
I got a UAF repport in tun driver when doing fuzzy test:
[ 466.269490] ================================================================== [ 466.271792] BUG: KASAN: use-after-free in tun_chr_read_iter+0x2ca/0x2d0 [ 466.271806] Read of size 8 at addr ffff888372139250 by task tun-test/2699 [ 466.271810] [ 466.271824] CPU: 1 PID: 2699 Comm: tun-test Not tainted 5.3.0-rc1-00001-g5a9433db2614-dirty #427 [ 466.271833] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 [ 466.271838] Call Trace: [ 466.271858] dump_stack+0xca/0x13e [ 466.271871] ? tun_chr_read_iter+0x2ca/0x2d0 [ 466.271890] print_address_description+0x79/0x440 [ 466.271906] ? vprintk_func+0x5e/0xf0 [ 466.271920] ? tun_chr_read_iter+0x2ca/0x2d0 [ 466.271935] __kasan_report+0x15c/0x1df [ 466.271958] ? tun_chr_read_iter+0x2ca/0x2d0 [ 466.271976] kasan_report+0xe/0x20 [ 466.271987] tun_chr_read_iter+0x2ca/0x2d0 [ 466.272013] do_iter_readv_writev+0x4b7/0x740 [ 466.272032] ? default_llseek+0x2d0/0x2d0 [ 466.272072] do_iter_read+0x1c5/0x5e0 [ 466.272110] vfs_readv+0x108/0x180 [ 466.299007] ? compat_rw_copy_check_uvector+0x440/0x440 [ 466.299020] ? fsnotify+0x888/0xd50 [ 466.299040] ? __fsnotify_parent+0xd0/0x350 [ 466.299064] ? fsnotify_first_mark+0x1e0/0x1e0 [ 466.304548] ? vfs_write+0x264/0x510 [ 466.304569] ? ksys_write+0x101/0x210 [ 466.304591] ? do_preadv+0x116/0x1a0 [ 466.304609] do_preadv+0x116/0x1a0 [ 466.309829] do_syscall_64+0xc8/0x600 [ 466.309849] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 466.309861] RIP: 0033:0x4560f9 [ 466.309875] Code: 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 [ 466.309889] RSP: 002b:00007ffffa5166e8 EFLAGS: 00000206 ORIG_RAX: 0000000000000127 [ 466.322992] RAX: ffffffffffffffda RBX: 0000000000400460 RCX: 00000000004560f9 [ 466.322999] RDX: 0000000000000003 RSI: 00000000200008c0 RDI: 0000000000000003 [ 466.323007] RBP: 00007ffffa516700 R08: 0000000000000004 R09: 0000000000000000 [ 466.323014] R10: 0000000000000000 R11: 0000000000000206 R12: 000000000040cb10 [ 466.323021] R13: 0000000000000000 R14: 00000000006d7018 R15: 0000000000000000 [ 466.323057] [ 466.323064] Allocated by task 2605: [ 466.335165] save_stack+0x19/0x80 [ 466.336240] __kasan_kmalloc.constprop.8+0xa0/0xd0 [ 466.337755] kmem_cache_alloc+0xe8/0x320 [ 466.339050] getname_flags+0xca/0x560 [ 466.340229] user_path_at_empty+0x2c/0x50 [ 466.341508] vfs_statx+0xe6/0x190 [ 466.342619] __do_sys_newstat+0x81/0x100 [ 466.343908] do_syscall_64+0xc8/0x600 [ 466.345303] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 466.347034] [ 466.347517] Freed by task 2605: [ 466.348471] save_stack+0x19/0x80 [ 466.349476] __kasan_slab_free+0x12e/0x180 [ 466.350726] kmem_cache_free+0xc8/0x430 [ 466.351874] putname+0xe2/0x120 [ 466.352921] filename_lookup+0x257/0x3e0 [ 466.354319] vfs_statx+0xe6/0x190 [ 466.355498] __do_sys_newstat+0x81/0x100 [ 466.356889] do_syscall_64+0xc8/0x600 [ 466.358037] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 466.359567] [ 466.360050] The buggy address belongs to the object at ffff888372139100 [ 466.360050] which belongs to the cache names_cache of size 4096 [ 466.363735] The buggy address is located 336 bytes inside of [ 466.363735] 4096-byte region [ffff888372139100, ffff88837213a100) [ 466.367179] The buggy address belongs to the page: [ 466.368604] page:ffffea000dc84e00 refcount:1 mapcount:0 mapping:ffff8883df1b4f00 index:0x0 compound_mapcount: 0 [ 466.371582] flags: 0x2fffff80010200(slab|head) [ 466.372910] raw: 002fffff80010200 dead000000000100 dead000000000122 ffff8883df1b4f00 [ 466.375209] raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000 [ 466.377778] page dumped because: kasan: bad access detected [ 466.379730] [ 466.380288] Memory state around the buggy address: [ 466.381844] ffff888372139100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 466.384009] ffff888372139180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 466.386131] >ffff888372139200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 466.388257] ^ [ 466.390234] ffff888372139280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 466.392512] ffff888372139300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 466.394667] ==================================================================
tun_chr_read_iter() accessed the memory which freed by free_netdev() called by tun_set_iff():
CPUA CPUB tun_set_iff() alloc_netdev_mqs() tun_attach() tun_chr_read_iter() tun_get() tun_do_read() tun_ring_recv() register_netdevice() <-- inject error goto err_detach tun_detach_all() <-- set RCV_SHUTDOWN free_netdev() <-- called from err_free_dev path netdev_freemem() <-- free the memory without check refcount (In this path, the refcount cannot prevent freeing the memory of dev, and the memory will be used by dev_put() called by tun_chr_read_iter() on CPUB.) (Break from tun_ring_recv(), because RCV_SHUTDOWN is set) tun_put() dev_put() <-- use the memory freed by netdev_freemem()
Put the publishing of tfile->tun after register_netdevice(), so tun_get() won't get the tun pointer that freed by err_detach path if register_netdevice() failed.
Fixes: eb0fb363f920 ("tuntap: attach queue 0 before registering netdevice") Reported-by: Hulk Robot hulkci@huawei.com Suggested-by: Jason Wang jasowang@redhat.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/tun.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-)
--- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -801,7 +801,8 @@ static void tun_detach_all(struct net_de }
static int tun_attach(struct tun_struct *tun, struct file *file, - bool skip_filter, bool napi, bool napi_frags) + bool skip_filter, bool napi, bool napi_frags, + bool publish_tun) { struct tun_file *tfile = file->private_data; struct net_device *dev = tun->dev; @@ -881,7 +882,8 @@ static int tun_attach(struct tun_struct * initialized tfile; otherwise we risk using half-initialized * object. */ - rcu_assign_pointer(tfile->tun, tun); + if (publish_tun) + rcu_assign_pointer(tfile->tun, tun); rcu_assign_pointer(tun->tfiles[tun->numqueues], tfile); tun->numqueues++; tun_set_real_num_queues(tun); @@ -2553,7 +2555,7 @@ static int tun_set_iff(struct net *net,
err = tun_attach(tun, file, ifr->ifr_flags & IFF_NOFILTER, ifr->ifr_flags & IFF_NAPI, - ifr->ifr_flags & IFF_NAPI_FRAGS); + ifr->ifr_flags & IFF_NAPI_FRAGS, true); if (err < 0) return err;
@@ -2652,13 +2654,17 @@ static int tun_set_iff(struct net *net,
INIT_LIST_HEAD(&tun->disabled); err = tun_attach(tun, file, false, ifr->ifr_flags & IFF_NAPI, - ifr->ifr_flags & IFF_NAPI_FRAGS); + ifr->ifr_flags & IFF_NAPI_FRAGS, false); if (err < 0) goto err_free_flow;
err = register_netdevice(tun->dev); if (err < 0) goto err_detach; + /* free_netdev() won't check refcnt, to aovid race + * with dev_put() we need publish tun after registration. + */ + rcu_assign_pointer(tfile->tun, tun); }
netif_carrier_on(tun->dev); @@ -2802,7 +2808,7 @@ static int tun_set_queue(struct file *fi if (ret < 0) goto unlock; ret = tun_attach(tun, file, false, tun->flags & IFF_NAPI, - tun->flags & IFF_NAPI_FRAGS); + tun->flags & IFF_NAPI_FRAGS, true); } else if (ifr->ifr_flags & IFF_DETACH_QUEUE) { tun = rtnl_dereference(tfile->tun); if (!tun || !(tun->flags & IFF_MULTI_QUEUE) || tfile->detached)