Hello, syzbot found the following issue on: HEAD commit: 7a695657 Add linux-next specific files for 20200903 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=15ac984e900000 kernel config: https://syzkaller.appspot.com/x/.config?x=39134fcec6c78e33 dashboard link: https://syzkaller.appspot.com/bug?extid=4264ecfcf0f27a5e4180 compiler: gcc (GCC) 10.1.0-syz 20200507 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13709f15900000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=147047e9900000 The issue was bisected to: commit d0c567d60f3730b97050347ea806e1ee06445c78 Author: Ming Lei <ming.lei@xxxxxxxxxx> Date: Wed Sep 2 12:26:42 2020 +0000 percpu_ref: reduce memory footprint of percpu_ref in fast path bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17ed5a95900000 final oops: https://syzkaller.appspot.com/x/report.txt?x=141d5a95900000 console output: https://syzkaller.appspot.com/x/log.txt?x=101d5a95900000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+4264ecfcf0f27a5e4180@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: d0c567d60f37 ("percpu_ref: reduce memory footprint of percpu_ref in fast path") ================================================================== BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:71 [inline] BUG: KASAN: null-ptr-deref in atomic64_read include/asm-generic/atomic-instrumented.h:837 [inline] BUG: KASAN: null-ptr-deref in atomic_long_read include/asm-generic/atomic-long.h:29 [inline] BUG: KASAN: null-ptr-deref in percpu_ref_exit+0x102/0x1f0 lib/percpu-refcount.c:136 Read of size 8 at addr 0000000000000000 by task syz-executor932/7175 CPU: 0 PID: 7175 Comm: syz-executor932 Not tainted 5.9.0-rc3-next-20200903-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+0x198/0x1fd lib/dump_stack.c:118 __kasan_report mm/kasan/report.c:517 [inline] kasan_report.cold+0x5/0x37 mm/kasan/report.c:530 check_memory_region_inline mm/kasan/generic.c:186 [inline] check_memory_region+0x13d/0x180 mm/kasan/generic.c:192 instrument_atomic_read include/linux/instrumented.h:71 [inline] atomic64_read include/asm-generic/atomic-instrumented.h:837 [inline] atomic_long_read include/asm-generic/atomic-long.h:29 [inline] percpu_ref_exit+0x102/0x1f0 lib/percpu-refcount.c:136 hd_free_part block/partitions/../blk.h:391 [inline] part_release+0x9d/0xc0 block/partitions/core.c:262 device_release+0x9f/0x240 drivers/base/core.c:1802 kobject_cleanup lib/kobject.c:708 [inline] kobject_release lib/kobject.c:739 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x171/0x270 lib/kobject.c:756 put_device+0x1b/0x30 drivers/base/core.c:3031 add_partition+0x648/0xb00 block/partitions/core.c:493 blk_add_partition block/partitions/core.c:685 [inline] blk_add_partitions+0x9db/0xe00 block/partitions/core.c:761 bdev_disk_changed+0x208/0x390 fs/block_dev.c:1417 loop_reread_partitions+0x29/0x50 drivers/block/loop.c:658 loop_set_status+0x6da/0x1010 drivers/block/loop.c:1427 loop_set_status64 drivers/block/loop.c:1547 [inline] lo_ioctl+0x900/0x1690 drivers/block/loop.c:1715 __blkdev_driver_ioctl block/ioctl.c:224 [inline] blkdev_ioctl+0x28c/0x700 block/ioctl.c:620 block_ioctl+0xf9/0x140 fs/block_dev.c:1870 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl fs/ioctl.c:739 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x446c27 Code: 48 83 c4 08 48 89 d8 5b 5d c3 66 0f 1f 84 00 00 00 00 00 48 89 e8 48 f7 d8 48 39 c3 0f 92 c0 eb 92 66 90 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 6d 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fb6aa64db48 EFLAGS: 00000202 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000446c27 RDX: 00007fb6aa64dbe0 RSI: 0000000000004c04 RDI: 0000000000000004 RBP: 00000000200158a8 R08: fe03f80fe03f80ff R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00007fb6aa64e6d0 R13: 0000000000000003 R14: 0000000000000003 R15: 000a00d800050102 ================================================================== --- This report 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 issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. For information about bisection process see: https://goo.gl/tpsmEJ#bisection syzbot can test patches for this issue, for details see: https://goo.gl/tpsmEJ#testing-patches
