Potential use-after-free in shrink_page_list

[Andrey Konovalov]

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!
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/