program syz-executor5 not setting count and/or reply_len properly
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BUG: KASAN: use-after-free in iov_iter_revert+0x976/0x9d0 lib/iov_iter.c:890
Read of size 4 at addr ffff8801d5e5bf78 by task loop0/11792

CPU: 1 PID: 11792 Comm: loop0 Not tainted 4.13.0-rc2+ #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 print_address_description+0x7f/0x260 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x24e/0x340 mm/kasan/report.c:408
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 iov_iter_revert+0x976/0x9d0 lib/iov_iter.c:890
 generic_file_read_iter+0x1874/0x26b0 mm/filemap.c:2186
 blkdev_read_iter+0x105/0x170 fs/block_dev.c:1917
 call_read_iter include/linux/fs.h:1737 [inline]
 lo_rw_aio+0x9e3/0xc20 drivers/block/loop.c:508
 do_req_filebacked drivers/block/loop.c:546 [inline]
 loop_handle_cmd drivers/block/loop.c:1724 [inline]
 loop_queue_work+0x1f91/0x3900 drivers/block/loop.c:1738
 kthread_worker_fn+0x4a0/0x970 kernel/kthread.c:635
 loop_kthread_worker_fn+0x51/0x60 drivers/block/loop.c:860
 kthread+0x35e/0x430 kernel/kthread.c:231
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:425

Allocated by task 13004:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xaa/0xd0 mm/kasan/kasan.c:551
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x101/0x6e0 mm/slab.c:3561
 mempool_alloc_slab+0x44/0x60 mm/mempool.c:449
 mempool_alloc+0x16a/0x4b0 mm/mempool.c:329
 bio_alloc_bioset+0x3c4/0x750 block/bio.c:486
 bio_alloc include/linux/bio.h:409 [inline]
 mpage_alloc+0x5c/0x1a0 fs/mpage.c:78
 do_mpage_readpage+0x1347/0x19e0 fs/mpage.c:285
 mpage_readpages+0x626/0x8a0 fs/mpage.c:382
 blkdev_readpages+0x2c/0x40 fs/block_dev.c:589
 read_pages mm/readahead.c:121 [inline]
 __do_page_cache_readahead+0x6c6/0xc00 mm/readahead.c:199
 force_page_cache_readahead+0x1fe/0x340 mm/readahead.c:232
 page_cache_sync_readahead+0xd0/0x100 mm/readahead.c:505
 do_generic_file_read mm/filemap.c:1939 [inline]
 generic_file_read_iter+0x163b/0x26b0 mm/filemap.c:2202
 blkdev_read_iter+0x105/0x170 fs/block_dev.c:1917
 call_read_iter include/linux/fs.h:1737 [inline]
 new_sync_read fs/read_write.c:400 [inline]
 __vfs_read+0x6a7/0xa00 fs/read_write.c:412
 vfs_read+0x11e/0x350 fs/read_write.c:433
 SYSC_read fs/read_write.c:549 [inline]
 SyS_read+0xef/0x220 fs/read_write.c:542
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 6119:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x6e/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3503 [inline]
 kmem_cache_free+0x71/0x240 mm/slab.c:3763
 mempool_free_slab+0x1d/0x30 mm/mempool.c:456
 mempool_free+0xd4/0x1d0 mm/mempool.c:438
 bio_free+0x114/0x190 block/bio.c:265
 bio_put+0x14f/0x180 block/bio.c:558
 mpage_end_io+0x13b/0x1a0 fs/mpage.c:57
 bio_endio+0x2e2/0x920 block/bio.c:1839
 req_bio_endio block/blk-core.c:204 [inline]
 blk_update_request+0x2a0/0xe10 block/blk-core.c:2729
 blk_mq_end_request+0x54/0x120 block/blk-mq.c:470
 lo_complete_rq+0xbe/0x1f0 drivers/block/loop.c:467
 __blk_mq_complete_request+0x396/0x6c0 block/blk-mq.c:511
 blk_mq_complete_request+0x22/0x30 block/blk-mq.c:531
 lo_rw_aio_complete+0x5e/0x80 drivers/block/loop.c:475
 blkdev_bio_end_io+0x224/0x6f0 fs/block_dev.c:309
 bio_endio+0x2e2/0x920 block/bio.c:1839
 req_bio_endio block/blk-core.c:204 [inline]
 blk_update_request+0x2a0/0xe10 block/blk-core.c:2729
 blk_mq_end_request+0x54/0x120 block/blk-mq.c:470
 lo_complete_rq+0xbe/0x1f0 drivers/block/loop.c:467
 __blk_mq_complete_request+0x396/0x6c0 block/blk-mq.c:511
 blk_mq_complete_request+0x22/0x30 block/blk-mq.c:531
 loop_handle_cmd drivers/block/loop.c:1729 [inline]
 loop_queue_work+0x26b/0x3900 drivers/block/loop.c:1738
 kthread_worker_fn+0x4a0/0x970 kernel/kthread.c:635
 loop_kthread_worker_fn+0x51/0x60 drivers/block/loop.c:860
 kthread+0x35e/0x430 kernel/kthread.c:231
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:425

The buggy address belongs to the object at ffff8801d5e5bf00
 which belongs to the cache bio-0 of size 176
The buggy address is located 120 bytes inside of
 176-byte region [ffff8801d5e5bf00, ffff8801d5e5bfb0)
The buggy address belongs to the page:
page:ffffea00066ca3e8 count:1 mapcount:0 mapping:ffff8801d5e5b000 index:0x0
flags: 0x200000000000100(slab)
raw: 0200000000000100 ffff8801d5e5b000 0000000000000000 0000000100000010
raw: ffffea0006660de8 ffffea00066c9480 ffff8801dae76300
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d5e5be00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d5e5be80: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
>ffff8801d5e5bf00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff8801d5e5bf80: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
 ffff8801d5e5c000: fb fb fb fb fb fb fb fb fc fc fc fc fb fb fb fb
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