Hello, syzbot found the following crash on: HEAD commit: f8788d86 Linux 5.6-rc3 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=13005fd9e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=9833e26bab355358 dashboard link: https://syzkaller.appspot.com/bug?extid=7dd7f2f77a7a01d1dc14 compiler: gcc (GCC) 9.0.0 20181231 (experimental) userspace arch: i386 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17e3ebede00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16a9f8f9e00000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+7dd7f2f77a7a01d1dc14@xxxxxxxxxxxxxxxxxxxxxxxxx ================================================================== BUG: KASAN: use-after-free in atomic_set include/asm-generic/atomic-instrumented.h:44 [inline] BUG: KASAN: use-after-free in refcount_set include/linux/refcount.h:123 [inline] BUG: KASAN: use-after-free in refcount_warn_saturate+0x1f/0x1f0 lib/refcount.c:15 Write of size 4 at addr ffff888090eb4018 by task kworker/1:24/2888 CPU: 1 PID: 2888 Comm: kworker/1:24 Not tainted 5.6.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events do_enable_set Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x197/0x210 lib/dump_stack.c:118 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374 __kasan_report.cold+0x1b/0x32 mm/kasan/report.c:506 kasan_report+0x12/0x20 mm/kasan/common.c:641 check_memory_region_inline mm/kasan/generic.c:185 [inline] check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192 __kasan_check_write+0x14/0x20 mm/kasan/common.c:101 atomic_set include/asm-generic/atomic-instrumented.h:44 [inline] refcount_set include/linux/refcount.h:123 [inline] refcount_warn_saturate+0x1f/0x1f0 lib/refcount.c:15 refcount_sub_and_test include/linux/refcount.h:261 [inline] refcount_dec_and_test include/linux/refcount.h:281 [inline] kref_put include/linux/kref.h:64 [inline] l2cap_chan_put+0x1d9/0x240 net/bluetooth/l2cap_core.c:498 do_enable_set+0x54b/0x960 net/bluetooth/6lowpan.c:1075 process_one_work+0xa05/0x17a0 kernel/workqueue.c:2264 worker_thread+0x98/0xe40 kernel/workqueue.c:2410 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Allocated by task 2888: save_stack+0x23/0x90 mm/kasan/common.c:72 set_track mm/kasan/common.c:80 [inline] __kasan_kmalloc mm/kasan/common.c:515 [inline] __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:488 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529 kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3551 kmalloc include/linux/slab.h:555 [inline] kzalloc include/linux/slab.h:669 [inline] l2cap_chan_create+0x45/0x3a0 net/bluetooth/l2cap_core.c:446 chan_create+0x10/0xe0 net/bluetooth/6lowpan.c:640 bt_6lowpan_listen net/bluetooth/6lowpan.c:959 [inline] do_enable_set+0x583/0x960 net/bluetooth/6lowpan.c:1078 process_one_work+0xa05/0x17a0 kernel/workqueue.c:2264 worker_thread+0x98/0xe40 kernel/workqueue.c:2410 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Freed by task 2975: save_stack+0x23/0x90 mm/kasan/common.c:72 set_track mm/kasan/common.c:80 [inline] kasan_set_free_info mm/kasan/common.c:337 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/common.c:476 kasan_slab_free+0xe/0x10 mm/kasan/common.c:485 __cache_free mm/slab.c:3426 [inline] kfree+0x10a/0x2c0 mm/slab.c:3757 l2cap_chan_destroy net/bluetooth/l2cap_core.c:484 [inline] kref_put include/linux/kref.h:65 [inline] l2cap_chan_put+0x1b7/0x240 net/bluetooth/l2cap_core.c:498 do_enable_set+0x54b/0x960 net/bluetooth/6lowpan.c:1075 process_one_work+0xa05/0x17a0 kernel/workqueue.c:2264 worker_thread+0x98/0xe40 kernel/workqueue.c:2410 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 The buggy address belongs to the object at ffff888090eb4000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 24 bytes inside of 2048-byte region [ffff888090eb4000, ffff888090eb4800) The buggy address belongs to the page: page:ffffea000243ad00 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0x0 flags: 0xfffe0000000200(slab) raw: 00fffe0000000200 ffffea0002694048 ffffea000241e648 ffff8880aa400e00 raw: 0000000000000000 ffff888090eb4000 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888090eb3f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888090eb3f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888090eb4000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888090eb4080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888090eb4100: 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
