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BUG: KASAN: use-after-free in bdev_nr_sectors include/linux/genhd.h:264 [inline]
BUG: KASAN: use-after-free in disk_part_iter_next+0x4c7/0x560 block/genhd.c:204
Read of size 8 at addr ffff888142695c28 by task syz-executor.0/13397

CPU: 1 PID: 13397 Comm: syz-executor.0 Not tainted 5.10.0-rc6-next-20201207-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:230
 __kasan_report mm/kasan/report.c:396 [inline]
 kasan_report.cold+0x79/0xd5 mm/kasan/report.c:413
 bdev_nr_sectors include/linux/genhd.h:264 [inline]
 disk_part_iter_next+0x4c7/0x560 block/genhd.c:204
 blk_drop_partitions+0x10a/0x180 block/partitions/core.c:541
 bdev_disk_changed+0x238/0x430 fs/block_dev.c:1228
 __loop_clr_fd+0x77b/0xe00 drivers/block/loop.c:1268
 lo_release+0x1ad/0x1f0 drivers/block/loop.c:1915
 __blkdev_put+0x54e/0x800 fs/block_dev.c:1570
 blkdev_put+0x92/0x5b0 fs/block_dev.c:1623
 blkdev_close+0x8c/0xb0 fs/block_dev.c:1631
 __fput+0x283/0x920 fs/file_table.c:280
 task_work_run+0xdd/0x190 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x1f0/0x200 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:302
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x417a51
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 a4 1a 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007f545dac8980 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000417a51
RDX: 0000000000000003 RSI: 0000000000004c00 RDI: 0000000000000004
RBP: 0000000000000000 R08: 00000000200006d8 R09: 0000000000000000
R10: 00000000060fffff R11: 0000000000000293 R12: 00007f545dac96d4
R13: 0000000000000010 R14: 0000000000000003 R15: 00000000200006e8

Allocated by task 10587:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:39
 kasan_set_track mm/kasan/common.c:47 [inline]
 set_alloc_info mm/kasan/common.c:405 [inline]
 ____kasan_kmalloc mm/kasan/common.c:436 [inline]
 ____kasan_kmalloc.constprop.0+0xa0/0xd0 mm/kasan/common.c:408
 kasan_slab_alloc include/linux/kasan.h:205 [inline]
 slab_post_alloc_hook mm/slab.h:518 [inline]
 slab_alloc_node mm/slub.c:2903 [inline]
 slab_alloc mm/slub.c:2911 [inline]
 kmem_cache_alloc+0x155/0x380 mm/slub.c:2916
 bdev_alloc_inode+0x18/0x40 fs/block_dev.c:777
 alloc_inode+0x61/0x230 fs/inode.c:233
 new_inode_pseudo fs/inode.c:927 [inline]
 new_inode+0x27/0x2f0 fs/inode.c:956
 bdev_alloc+0x20/0x340 fs/block_dev.c:864
 add_partition+0x1ad/0x8e0 block/partitions/core.c:345
 bdev_add_partition+0xb6/0x130 block/partitions/core.c:449
 blkpg_do_ioctl+0x2d0/0x340 block/ioctl.c:43
 blkpg_ioctl block/ioctl.c:60 [inline]
 blkdev_ioctl+0x577/0x6d0 block/ioctl.c:541
 block_ioctl+0xf9/0x140 fs/block_dev.c:1649
 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

Freed by task 13386:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:39
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:47
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:355
 ____kasan_slab_free.part.0+0xe1/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:188 [inline]
 slab_free_hook mm/slub.c:1548 [inline]
 slab_free_freelist_hook+0x82/0x1d0 mm/slub.c:1586
 slab_free mm/slub.c:3157 [inline]
 kmem_cache_free+0x82/0x360 mm/slub.c:3173
 i_callback+0x3f/0x70 fs/inode.c:222
 rcu_do_batch kernel/rcu/tree.c:2502 [inline]
 rcu_core+0x735/0x1020 kernel/rcu/tree.c:2737
 __do_softirq+0x2b7/0xa76 kernel/softirq.c:343

Last potentially related work creation:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:39
 kasan_record_aux_stack+0xdc/0x100 mm/kasan/generic.c:343
 __call_rcu kernel/rcu/tree.c:2987 [inline]
 call_rcu+0xbb/0x810 kernel/rcu/tree.c:3062
 destroy_inode+0x129/0x1b0 fs/inode.c:288
 iput_final fs/inode.c:1651 [inline]
 iput.part.0+0x41e/0x840 fs/inode.c:1677
 iput+0x58/0x70 fs/inode.c:1667
 disk_part_iter_exit block/genhd.c:232 [inline]
 disk_part_iter_next+0x9a/0x560 block/genhd.c:200
 blk_drop_partitions+0x10a/0x180 block/partitions/core.c:541
 bdev_disk_changed+0x238/0x430 fs/block_dev.c:1228
 loop_reread_partitions+0x29/0x50 drivers/block/loop.c:655
 loop_set_status+0x735/0x1040 drivers/block/loop.c:1416
 loop_set_status64 drivers/block/loop.c:1536 [inline]
 lo_ioctl+0x900/0x1720 drivers/block/loop.c:1704
 blkdev_ioctl+0x2a1/0x6d0 block/ioctl.c:576
 block_ioctl+0xf9/0x140 fs/block_dev.c:1649
 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

The buggy address belongs to the object at ffff888142695c00
 which belongs to the cache bdev_cache of size 2808
The buggy address is located 40 bytes inside of
 2808-byte region [ffff888142695c00, ffff8881426966f8)
The buggy address belongs to the page:
page:00000000e3bc4565 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x142690
head:00000000e3bc4565 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x57ff00000010200(slab|head)
raw: 057ff00000010200 dead000000000100 dead000000000122 ffff888140006b40
raw: 0000000000000000 00000000800b000b 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888142695b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc
 ffff888142695b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888142695c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff888142695c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888142695d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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