On Fri, Jul 31, 2020 at 02:11:22PM -0700, Rustam Kovhaev wrote: > On Thu, Jul 09, 2020 at 04:54:19PM -0700, syzbot wrote: > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: 0bddd227 Documentation: update for gcc 4.9 requirement > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=1418afb7100000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=66ad203c2bb6d8b > > dashboard link: https://syzkaller.appspot.com/bug?extid=20b90969babe05609947 > > compiler: gcc (GCC) 10.1.0-syz 20200507 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12a8edff100000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=167d3bb7100000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+20b90969babe05609947@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ================================================================== > > BUG: KASAN: use-after-free in dev_put include/linux/netdevice.h:3853 [inline] > > BUG: KASAN: use-after-free in netdevice_event_work_handler+0x15b/0x1b0 drivers/infiniband/core/roce_gid_mgmt.c:627 > > Read of size 8 at addr ffff88807b13e568 by task kworker/u4:0/7 > > > > CPU: 0 PID: 7 Comm: kworker/u4:0 Not tainted 5.8.0-rc4-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Workqueue: gid-cache-wq netdevice_event_work_handler > > Call Trace: > > __dump_stack lib/dump_stack.c:77 [inline] > > dump_stack+0x18f/0x20d lib/dump_stack.c:118 > > print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383 > > __kasan_report mm/kasan/report.c:513 [inline] > > kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530 > > dev_put include/linux/netdevice.h:3853 [inline] > > netdevice_event_work_handler+0x15b/0x1b0 drivers/infiniband/core/roce_gid_mgmt.c:627 > > process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 > > worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 > > kthread+0x3b5/0x4a0 kernel/kthread.c:291 > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293 > > > > Allocated by task 13061: > > save_stack+0x1b/0x40 mm/kasan/common.c:48 > > set_track mm/kasan/common.c:56 [inline] > > __kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494 > > kmalloc_node include/linux/slab.h:578 [inline] > > kvmalloc_node+0x61/0xf0 mm/util.c:574 > > kvmalloc include/linux/mm.h:753 [inline] > > kvzalloc include/linux/mm.h:761 [inline] > > alloc_netdev_mqs+0x97/0xdc0 net/core/dev.c:9938 > > __ip_tunnel_create+0x201/0x580 net/ipv4/ip_tunnel.c:254 > > ip_tunnel_init_net+0x32b/0x980 net/ipv4/ip_tunnel.c:1072 > > ops_init+0xaf/0x470 net/core/net_namespace.c:151 > > setup_net+0x2d8/0x850 net/core/net_namespace.c:341 > > copy_net_ns+0x2cf/0x5e0 net/core/net_namespace.c:482 > > create_new_namespaces+0x3f6/0xb10 kernel/nsproxy.c:110 > > unshare_nsproxy_namespaces+0xbd/0x1f0 kernel/nsproxy.c:231 > > ksys_unshare+0x36c/0x9a0 kernel/fork.c:2983 > > __do_sys_unshare kernel/fork.c:3051 [inline] > > __se_sys_unshare kernel/fork.c:3049 [inline] > > __x64_sys_unshare+0x2d/0x40 kernel/fork.c:3049 > > do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384 > > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > Freed by task 13061: > > save_stack+0x1b/0x40 mm/kasan/common.c:48 > > set_track mm/kasan/common.c:56 [inline] > > kasan_set_free_info mm/kasan/common.c:316 [inline] > > __kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455 > > __cache_free mm/slab.c:3426 [inline] > > kfree+0x103/0x2c0 mm/slab.c:3757 > > kvfree+0x42/0x50 mm/util.c:603 > > device_release+0x71/0x200 drivers/base/core.c:1559 > > kobject_cleanup lib/kobject.c:693 [inline] > > kobject_release lib/kobject.c:722 [inline] > > kref_put include/linux/kref.h:65 [inline] > > kobject_put+0x1c0/0x270 lib/kobject.c:739 > > put_device+0x1b/0x30 drivers/base/core.c:2779 > > free_netdev+0x35d/0x480 net/core/dev.c:10054 > > __ip_tunnel_create+0x48f/0x580 net/ipv4/ip_tunnel.c:274 > > ip_tunnel_init_net+0x32b/0x980 net/ipv4/ip_tunnel.c:1072 > > ops_init+0xaf/0x470 net/core/net_namespace.c:151 > > setup_net+0x2d8/0x850 net/core/net_namespace.c:341 > > copy_net_ns+0x2cf/0x5e0 net/core/net_namespace.c:482 > > create_new_namespaces+0x3f6/0xb10 kernel/nsproxy.c:110 > > unshare_nsproxy_namespaces+0xbd/0x1f0 kernel/nsproxy.c:231 > > ksys_unshare+0x36c/0x9a0 kernel/fork.c:2983 > > __do_sys_unshare kernel/fork.c:3051 [inline] > > __se_sys_unshare kernel/fork.c:3049 [inline] > > __x64_sys_unshare+0x2d/0x40 kernel/fork.c:3049 > > do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384 > > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > The buggy address belongs to the object at ffff88807b13e000 > > which belongs to the cache kmalloc-4k of size 4096 > > The buggy address is located 1384 bytes inside of > > 4096-byte region [ffff88807b13e000, ffff88807b13f000) > > The buggy address belongs to the page: > > page:ffffea0001ec4f80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 head:ffffea0001ec4f80 order:1 compound_mapcount:0 > > flags: 0xfffe0000010200(slab|head) > > raw: 00fffe0000010200 ffffea0001ecce88 ffffea0001987988 ffff8880aa002000 > > raw: 0000000000000000 ffff88807b13e000 0000000100000001 0000000000000000 > > page dumped because: kasan: bad access detected > > > > Memory state around the buggy address: > > ffff88807b13e400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ffff88807b13e480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > >ffff88807b13e500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ^ > > ffff88807b13e580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ffff88807b13e600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ================================================================== > > > > > > --- > > This bug is generated by a bot. It may contain errors. > > See https://goo.gl/tpsmEJ for more information about syzbot. > > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > > > syzbot will keep track of this bug report. See: > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > syzbot can test patches for this bug, for details see: > > https://goo.gl/tpsmEJ#testing-patches > > IB roce driver receives NETDEV_UNREGISTER event, calls dev_hold() and > schedules work item to execute, and before wq gets a chance to complete > it, we return to ip_tunnel.c:274 and call free_netdev(), and then later > we get UAF when scheduled function references already freed net_device > > i added verbose logging to ip_tunnel.c to see pcpu_refcnt: > + pr_info("about to free_netdev(dev) dev->pcpu_refcnt %d", netdev_refcnt_read(dev)); > > and got the following: > [ 410.220127][ T2944] ip_tunnel: about to free_netdev(dev) dev->pcpu_refcnt 8 > > i tried to make IB roce driver flush wq and work item, but i ran into > lockdep issues > also tried to modify dev core and call netdev_wait_allrefs() but ran > into rntl deadlocks > > any hints or help in fixing this would be appreciated, thank you! > does the patch below look sane to you? or is it complete nonsense? syzbot test came out OK, but it might not mean anything diff --git a/drivers/infiniband/core/roce_gid_mgmt.c b/drivers/infiniband/core/roce_gid_mgmt.c index 2860def84f4d..b31c8969c8b2 100644 --- a/drivers/infiniband/core/roce_gid_mgmt.c +++ b/drivers/infiniband/core/roce_gid_mgmt.c @@ -626,6 +626,7 @@ static void netdevice_event_work_handler(struct work_struct *_work) work->cmds[i].ndev); dev_put(work->cmds[i].ndev); dev_put(work->cmds[i].filter_ndev); + put_device(&work->cmds[i].ndev->dev); } kfree(work); @@ -649,6 +650,7 @@ static int netdevice_queue_work(struct netdev_event_work_cmd *cmds, ndev_work->cmds[i].filter_ndev = ndev; dev_hold(ndev_work->cmds[i].ndev); dev_hold(ndev_work->cmds[i].filter_ndev); + get_device(&ndev_work->cmds[i].ndev->dev); } INIT_WORK(&ndev_work->work, netdevice_event_work_handler);
