On Thu, May 28, 2020 at 07:33:16AM -0700, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: c11d28ab Add linux-next specific files for 20200522 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=12fc3e72100000 > kernel config: https://syzkaller.appspot.com/x/.config?x=3f6dbdea4159fb66 > dashboard link: https://syzkaller.appspot.com/bug?extid=478fd0d54412b8759e0d > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+478fd0d54412b8759e0d@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================== > BUG: KASAN: use-after-free in ib_uverbs_remove_one+0x411/0x4e0 drivers/infiniband/core/uverbs_main.c:1210 > Read of size 4 at addr ffff888096324578 by task syz-executor.2/15847 > > CPU: 1 PID: 15847 Comm: syz-executor.2 Not tainted 5.7.0-rc6-next-20200522-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > 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+0xd3/0x413 mm/kasan/report.c:383 > __kasan_report mm/kasan/report.c:513 [inline] > kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530 > ib_uverbs_remove_one+0x411/0x4e0 drivers/infiniband/core/uverbs_main.c:1210 > remove_client_context+0xbe/0x110 drivers/infiniband/core/device.c:732 > disable_device+0x13b/0x230 drivers/infiniband/core/device.c:1278 > __ib_unregister_device+0x91/0x180 drivers/infiniband/core/device.c:1445 > ib_unregister_device_and_put+0x57/0x80 drivers/infiniband/core/device.c:1508 > nldev_dellink+0x20a/0x310 drivers/infiniband/core/nldev.c:1571 > rdma_nl_rcv_msg drivers/infiniband/core/netlink.c:195 [inline] > rdma_nl_rcv_skb drivers/infiniband/core/netlink.c:239 [inline] > rdma_nl_rcv+0x586/0x900 drivers/infiniband/core/netlink.c:259 > netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline] > netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329 > netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918 > sock_sendmsg_nosec net/socket.c:652 [inline] > sock_sendmsg+0xcf/0x120 net/socket.c:672 > ____sys_sendmsg+0x6e6/0x810 net/socket.c:2352 > ___sys_sendmsg+0x100/0x170 net/socket.c:2406 > __sys_sendmsg+0xe5/0x1b0 net/socket.c:2439 > do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 > entry_SYSCALL_64_after_hwframe+0x49/0xb3 > RIP: 0033:0x45ca29 > Code: 0d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007fd6764d1c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e > RAX: ffffffffffffffda RBX: 00000000004ffa00 RCX: 000000000045ca29 > RDX: 0000000000000000 RSI: 0000000020000180 RDI: 0000000000000003 > RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff > R13: 00000000000009af R14: 00000000004d61b0 R15: 00007fd6764d26d4 > > Allocated by task 9061: > save_stack+0x1b/0x40 mm/kasan/common.c:48 > set_track mm/kasan/common.c:56 [inline] > __kasan_kmalloc mm/kasan/common.c:494 [inline] > __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:467 > kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551 > kmalloc include/linux/slab.h:555 [inline] > kzalloc include/linux/slab.h:669 [inline] > ib_uverbs_add_one+0x80/0x7c0 drivers/infiniband/core/uverbs_main.c:1107 > add_client_context+0x400/0x5e0 drivers/infiniband/core/device.c:677 > enable_device_and_get+0x1cd/0x3b0 drivers/infiniband/core/device.c:1326 > ib_register_device drivers/infiniband/core/device.c:1392 [inline] > ib_register_device+0xa12/0xda0 drivers/infiniband/core/device.c:1353 > siw_device_register drivers/infiniband/sw/siw/siw_main.c:70 [inline] > siw_newlink drivers/infiniband/sw/siw/siw_main.c:565 [inline] > siw_newlink+0xd37/0x1240 drivers/infiniband/sw/siw/siw_main.c:542 > nldev_newlink+0x29e/0x420 drivers/infiniband/core/nldev.c:1541 > rdma_nl_rcv_msg drivers/infiniband/core/netlink.c:195 [inline] > rdma_nl_rcv_skb drivers/infiniband/core/netlink.c:239 [inline] > rdma_nl_rcv+0x586/0x900 drivers/infiniband/core/netlink.c:259 > netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline] > netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329 > netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918 > sock_sendmsg_nosec net/socket.c:652 [inline] > sock_sendmsg+0xcf/0x120 net/socket.c:672 > ____sys_sendmsg+0x6e6/0x810 net/socket.c:2352 > ___sys_sendmsg+0x100/0x170 net/socket.c:2406 > __sys_sendmsg+0xe5/0x1b0 net/socket.c:2439 > do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 > entry_SYSCALL_64_after_hwframe+0x49/0xb3 > > Freed by task 15847: > 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+0xf7/0x140 mm/kasan/common.c:455 > __cache_free mm/slab.c:3426 [inline] > kfree+0x109/0x2b0 mm/slab.c:3757 > device_release+0x71/0x200 drivers/base/core.c:1541 > kobject_cleanup lib/kobject.c:701 [inline] > kobject_release lib/kobject.c:732 [inline] > kref_put include/linux/kref.h:65 [inline] > kobject_put+0x1c8/0x2f0 lib/kobject.c:749 > cdev_device_del+0x69/0x80 fs/char_dev.c:575 > ib_uverbs_remove_one+0x31/0x4e0 drivers/infiniband/core/uverbs_main.c:1209 I still can't figure out how this is possible, but I can say cdev_device_del should not be freeing this memory - it can only mean the uverbs_dev->dev.kref has become put several more times than it should have. Hopefully syzkaller will hit a refcount underflow and tell us where as I checked every put_device obviously connected to uverbs_dev and found nothing.. Jason
