Hi!
While fuzzing the kernel (4.3-rc4) with KASAN and Trinity I got the
following report:
==================================================================
BUG: KASan: use after free in shrink_page_list+0x93a/0xf10 at addr
ffff88003487da80
Read of size 8 by task kswapd0/622
=============================================================================
BUG kmalloc-16 (Not tainted): kasan: bad access detected
-----------------------------------------------------------------------------
Disabling lock debugging due to kernel taint
INFO: Allocated in bdi_init+0xb9/0x480 age=235622 cpu=0 pid=6
[< none >] __slab_alloc+0x44a/0x480 mm/slub.c:2402
[< inline >] slab_alloc mm/slub.c:2470
[< none >] kmem_cache_alloc_trace+0x12a/0x160 mm/slub.c:2529
[< inline >] kmalloc include/linux/slab.h:440
[< inline >] kzalloc include/linux/slab.h:593
[< inline >] cgwb_bdi_init mm/backing-dev.c:749
[< none >] bdi_init+0xb9/0x480 mm/backing-dev.c:775
[< none >] blk_alloc_queue_node+0xfc/0x380 block/blk-core.c:656
[< none >] blk_init_queue_node+0x1f/0x60 block/blk-core.c:754
[< none >] blk_init_queue+0xe/0x10 block/blk-core.c:745
[< none >] __scsi_alloc_queue+0x14/0x30 drivers/scsi/scsi_lib.c:2139
[< none >] scsi_alloc_queue+0x1c/0x80 drivers/scsi/scsi_lib.c:2151
[< none >] scsi_alloc_sdev+0x3cd/0x5f0 scsi_scan.c:0
[< none >] scsi_probe_and_add_lun+0xc3a/0x10a0 scsi_scan.c:0
[< none >] __scsi_add_device+0x112/0x120 ??:0
[< none >] ata_scsi_scan_host+0xed/0x260 ??:0
[< none >] async_port_probe+0x61/0x80 drivers/ata/libata-core.c:6097
[< none >] async_run_entry_fn+0x74/0x190 async.c:0
[< none >] process_one_work+0x276/0x630 kernel/workqueue.c:2030
[< none >] worker_thread+0x98/0x720 kernel/workqueue.c:2162
INFO: Freed in bdi_destroy+0x1d9/0x200 age=1073 cpu=0 pid=5919
[< none >] __slab_free+0x150/0x270 mm/slub.c:2587
[< inline >] slab_free mm/slub.c:2736
[< none >] kfree+0x13a/0x150 mm/slub.c:3522
[< inline >] wb_exit include/linux/backing-dev.h:483
[< none >] bdi_destroy+0x1d9/0x200 mm/backing-dev.c:839
[< none >] blk_cleanup_queue+0x158/0x190 block/blk-core.c:579
[< none >] __scsi_remove_device+0x63/0x110 ??:0
[< none >] scsi_remove_device+0x27/0x40 ??:0
[< none >] sdev_store_delete+0x22/0x30 scsi_sysfs.c:0
[< none >] dev_attr_store+0x39/0x50 drivers/base/core.c:137
[< none >] sysfs_kf_write+0x8a/0xa0 file.c:0
[< none >] kernfs_fop_write+0x167/0x200 file.c:0
[< none >] __vfs_write+0x57/0x170 ??:0
[< none >] vfs_write+0xeb/0x250 ??:0
[< none >] SyS_write+0x53/0xb0 ??:0
[< none >] entry_SYSCALL_64_fastpath+0x12/0x71
arch/x86/entry/entry_64.S:185
INFO: Slab 0xffffea0000d21f40 objects=12 used=4 fp=0xffff88003487d3f0
flags=0x100000000000080
INFO: Object 0xffff88003487da80 @offset=2688 fp=0x (null)
Bytes b4 ffff88003487da70: a3 08 ff ff 00 00 00 00 aa 18 57 81 ff ff
ff ff ..........W.....
Object ffff88003487da80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 ................
Redzone ffff88003487da90: bb bb bb bb bb bb bb bb
........
Padding ffff88003487dbc8: 84 d5 76 81 ff ff ff ff
..v.....
CPU: 0 PID: 622 Comm: kswapd0 Tainted: G B 4.3.0-rc4-kasan #16
Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2007
ffff88003487da80 ffff880034c0f878 ffffffff814a3e7c ffff880036003b00
ffff880034c0f8a8 ffffffff812090b8 ffff880036003b00 ffffea0000d21f40
ffff88003487da80 ffffea0000ceaf98 ffff880034c0f8d0 ffffffff8120def1
Call Trace:
[<ffffffff814a3e7c>] dump_stack+0x44/0x58 lib/dump_stack.c:15
[<ffffffff812090b8>] print_trailer+0xf8/0x150 mm/slub.c:650
[<ffffffff8120def1>] object_err+0x31/0x40 mm/slub.c:657
[<ffffffff81210215>] kasan_report_error+0x1e5/0x3f0 ??:0
[<ffffffff81210804>] kasan_report+0x34/0x40 ??:0
[< inline >] ? inode_write_congested include/linux/backing-dev.h:193
[<ffffffff811bcc1a>] ? shrink_page_list+0x93a/0xf10 mm/vmscan.c:957
[<ffffffff8120f564>] __asan_load8+0x64/0xa0 ??:0
[<ffffffff811c814f>] ? page_mapping+0x2f/0x70 ??:0
[< inline >] inode_write_congested include/linux/backing-dev.h:193
[<ffffffff811bcc1a>] shrink_page_list+0x93a/0xf10 mm/vmscan.c:957
[<ffffffff811bda74>] shrink_inactive_list+0x2f4/0x5f0 mm/vmscan.c:1610
[< inline >] shrink_list mm/vmscan.c:1945
[<ffffffff811bea0a>] shrink_lruvec+0x87a/0xa50 mm/vmscan.c:2229
[<ffffffff811beca0>] shrink_zone+0xc0/0x2c0 mm/vmscan.c:2413
[< inline >] kswapd_shrink_zone mm/vmscan.c:3116
[< inline >] balance_pgdat mm/vmscan.c:3291
[<ffffffff811bffad>] kswapd+0x64d/0xb70 mm/vmscan.c:3499
[<ffffffff811bf960>] ? zone_reclaim+0x2a0/0x2a0 mm/vmscan.c:3820
[<ffffffff810a491f>] kthread+0x10f/0x130 kthread.c:0
[<ffffffff810a4810>] ? kthread_park+0x70/0x70 ??:0
[<ffffffff81d4fb5f>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:472
[<ffffffff810a4810>] ? kthread_park+0x70/0x70 ??:0
Memory state around the buggy address:
ffff88003487d980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88003487da00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88003487da80: fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff88003487db00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88003487db80: fc fc fc fc fc fc fc fc fc fc 00 00 fc fc fc fc
==================================================================
Thanks!
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