Date:   Mon, 25 Nov 2019 10:28:54 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Qian Cai <cai@....pw>, Joerg Roedel <jroedel@...e.de>
Cc:     Christoph Hellwig <hch@....de>, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: "Revisit iommu_insert_resv_region() implementation" causes
 use-after-free

Hi,

On 11/22/19 4:06 PM, Qian Cai wrote:
> Read files under /sys/kernel/iommu_groups/ triggers an use-after-free. Reverted
> the commit 4dbd258ff63e ("iommu: Revisit iommu_insert_resv_region()
> implementation") fixed the issue.
> 
> /* no merge needed on elements of different types than @nr */
> if (iter->type != nr->type) {
> 	list_move_tail(&iter->list, &stack);
> 	continue;

OK I have just got it, nr->type is the cause. I will send a patch asap

Thanks

Eric
> 
> [  160.156964][ T3100] BUG: KASAN: use-after-free in
> iommu_insert_resv_region+0x34b/0x520
> [  160.197758][ T3100] Read of size 4 at addr ffff8887aba78464 by task cat/3100
> [  160.230645][ T3100] 
> [  160.240907][ T3100] CPU: 14 PID: 3100 Comm: cat Not tainted 5.4.0-rc8-next-
> 20191122+ #11
> [  160.278671][ T3100] Hardware name: HP ProLiant XL420 Gen9/ProLiant XL420
> Gen9, BIOS U19 12/27/2015
> [  160.320589][ T3100] Call Trace:
> [  160.335229][ T3100]  dump_stack+0xa0/0xea
> [  160.354011][ T3100]  print_address_description.constprop.5.cold.7+0x9/0x384
> [  160.386569][ T3100]  __kasan_report.cold.8+0x7a/0xc0
> [  160.409811][ T3100]  ? iommu_insert_resv_region+0x34b/0x520
> [  160.435668][ T3100]  kasan_report+0x12/0x20
> [  160.455387][ T3100]  __asan_load4+0x95/0xa0
> [  160.474808][ T3100]  iommu_insert_resv_region+0x34b/0x520
> [  160.500228][ T3100]  ? iommu_bus_notifier+0xe0/0xe0
> [  160.522904][ T3100]  ? intel_iommu_get_resv_regions+0x348/0x400
> [  160.550461][ T3100]  iommu_get_group_resv_regions+0x16d/0x2f0
> [  160.577611][ T3100]  ? iommu_insert_resv_region+0x520/0x520
> [  160.603756][ T3100]  ? register_lock_class+0x940/0x940
> [  160.628265][ T3100]  iommu_group_show_resv_regions+0x8d/0x1f0
> [  160.655370][ T3100]  ? iommu_get_group_resv_regions+0x2f0/0x2f0
> [  160.684168][ T3100]  iommu_group_attr_show+0x34/0x50
> [  160.708395][ T3100]  sysfs_kf_seq_show+0x11c/0x220
> [  160.731758][ T3100]  ? iommu_default_passthrough+0x20/0x20
> [  160.756898][ T3100]  kernfs_seq_show+0xa4/0xb0
> [  160.777097][ T3100]  seq_read+0x27e/0x710
> [  160.795195][ T3100]  kernfs_fop_read+0x7d/0x2c0
> [  160.815349][ T3100]  __vfs_read+0x50/0xa0
> [  160.834154][ T3100]  vfs_read+0xcb/0x1e0
> [  160.852332][ T3100]  ksys_read+0xc6/0x160
> [  160.871028][ T3100]  ? kernel_write+0xc0/0xc0
> [  160.891307][ T3100]  ? do_syscall_64+0x79/0xaec
> [  160.912446][ T3100]  ? do_syscall_64+0x79/0xaec
> [  160.933640][ T3100]  __x64_sys_read+0x43/0x50
> [  160.953957][ T3100]  do_syscall_64+0xcc/0xaec
> [  160.974322][ T3100]  ? trace_hardirqs_on_thunk+0x1a/0x1c
> [  160.999130][ T3100]  ? syscall_return_slowpath+0x580/0x580
> [  161.024753][ T3100]  ? entry_SYSCALL_64_after_hwframe+0x3e/0xbe
> [  161.052416][ T3100]  ? trace_hardirqs_off_caller+0x3a/0x150
> [  161.078400][ T3100]  ? trace_hardirqs_off_thunk+0x1a/0x1c
> [  161.103711][ T3100]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [  161.130793][ T3100] RIP: 0033:0x7f33e0d89d75
> [  161.150732][ T3100] Code: fe ff ff 50 48 8d 3d 4a dc 09 00 e8 25 0e 02 00 0f
> 1f 44 00 00 f3 0f 1e fa 48 8d 05 a5 59 2d 00 8b 00 85 c0 75 0f 31 c0 0f 05 <48>
> 3d 00 f0 ff ff 77 53 c3 66 90 41 54 49 89 d4 55 48 89 f5 53 89
> [  161.245503][ T3100] RSP: 002b:00007fff88f0db88 EFLAGS: 00000246 ORIG_RAX:
> 0000000000000000
> [  161.284547][ T3100] RAX: ffffffffffffffda RBX: 0000000000020000 RCX:
> 00007f33e0d89d75
> [  161.321123][ T3100] RDX: 0000000000020000 RSI: 00007f33e1201000 RDI:
> 0000000000000003
> [  161.357617][ T3100] RBP: 00007f33e1201000 R08: 00000000ffffffff R09:
> 0000000000000000
> [  161.394173][ T3100] R10: 0000000000000022 R11: 0000000000000246 R12:
> 00007f33e1201000
> [  161.430736][ T3100] R13: 0000000000000003 R14: 0000000000000fff R15:
> 0000000000020000
> [  161.467337][ T3100] 
> [  161.477529][ T3100] Allocated by task 3100:
> [  161.497133][ T3100]  save_stack+0x21/0x90
> [  161.515777][ T3100]  __kasan_kmalloc.constprop.13+0xc1/0xd0
> [  161.541743][ T3100]  kasan_kmalloc+0x9/0x10
> [  161.561330][ T3100]  kmem_cache_alloc_trace+0x1f8/0x470
> [  161.585949][ T3100]  iommu_insert_resv_region+0xeb/0x520
> [  161.610876][ T3100]  iommu_get_group_resv_regions+0x16d/0x2f0
> [  161.638318][ T3100]  iommu_group_show_resv_regions+0x8d/0x1f0
> [  161.665322][ T3100]  iommu_group_attr_show+0x34/0x50
> [  161.688526][ T3100]  sysfs_kf_seq_show+0x11c/0x220
> [  161.711992][ T3100]  kernfs_seq_show+0xa4/0xb0
> [  161.734252][ T3100]  seq_read+0x27e/0x710
> [  161.754412][ T3100]  kernfs_fop_read+0x7d/0x2c0
> [  161.775493][ T3100]  __vfs_read+0x50/0xa0
> [  161.794328][ T3100]  vfs_read+0xcb/0x1e0
> [  161.812559][ T3100]  ksys_read+0xc6/0x160
> [  161.831554][ T3100]  __x64_sys_read+0x43/0x50
> [  161.851772][ T3100]  do_syscall_64+0xcc/0xaec
> [  161.872098][ T3100]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [  161.898919][ T3100] 
> [  161.909113][ T3100] Freed by task 3100:
> [  161.927070][ T3100]  save_stack+0x21/0x90
> [  161.945711][ T3100]  __kasan_slab_free+0x11c/0x170
> [  161.968112][ T3100]  kasan_slab_free+0xe/0x10
> [  161.988601][ T3100]  slab_free_freelist_hook+0x5f/0x1d0
> [  162.012918][ T3100]  kfree+0xe9/0x410
> [  162.029454][ T3100]  iommu_insert_resv_region+0x47d/0x520
> [  162.053701][ T3100]  iommu_get_group_resv_regions+0x16d/0x2f0
> [  162.079671][ T3100]  iommu_group_show_resv_regions+0x8d/0x1f0
> [  162.105484][ T3100]  iommu_group_attr_show+0x34/0x50
> [  162.127709][ T3100]  sysfs_kf_seq_show+0x11c/0x220
> [  162.149250][ T3100]  kernfs_seq_show+0xa4/0xb0
> [  162.169085][ T3100]  seq_read+0x27e/0x710
> [  162.187038][ T3100]  kernfs_fop_read+0x7d/0x2c0
> [  162.207391][ T3100]  __vfs_read+0x50/0xa0
> [  162.227829][ T3100]  vfs_read+0xcb/0x1e0
> [  162.247788][ T3100]  ksys_read+0xc6/0x160
> [  162.265471][ T3100]  __x64_sys_read+0x43/0x50
> [  162.285041][ T3100]  do_syscall_64+0xcc/0xaec
> [  162.304627][ T3100]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [  162.330429][ T3100] 
> [  162.340199][ T3100] The buggy address belongs to the object at
> ffff8887aba78440
> [  162.340199][ T3100]  which belongs to the cache kmalloc-64 of size 64
> [  162.402050][ T3100] The buggy address is located 36 bytes inside of
> [  162.402050][ T3100]  64-byte region [ffff8887aba78440, ffff8887aba78480)
> [  162.460127][ T3100] The buggy address belongs to the page:
> [  162.484696][ T3100] page:ffffea001eae9e00 refcount:1 mapcount:0
> mapping:ffff888207c02ac0 index:0xffff8887aba78e40
> [  162.531045][ T3100] raw: 015fffe000000200 ffff888487c00740 ffff888487c00740
> ffff888207c02ac0
> [  162.569455][ T3100] raw: ffff8887aba78e40 0000000000080003 00000001ffffffff
> 0000000000000000
> [  162.607801][ T3100] page dumped because: kasan: bad access detected
> [  162.636603][ T3100] page_owner tracks the page as allocated
> [  162.661634][ T3100] page last allocated via order 0, migratetype Unmovable,
> gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY)
> [  162.716310][ T3100]  prep_new_page+0x2ed/0x310
> [  162.739158][ T3100]  get_page_from_freelist+0x20bb/0x3090
> [  162.765017][ T3100]  __alloc_pages_nodemask+0x2e4/0x720
> [  162.788440][ T3100]  alloc_pages_current+0x9c/0x110
> [  162.810324][ T3100]  alloc_slab_page+0xc9/0x4e0
> [  162.831044][ T3100]  allocate_slab+0x70/0x5d0
> [  162.851450][ T3100]  new_slab+0x46/0x70
> [  162.869326][ T3100]  ___slab_alloc+0x4ab/0x7b0
> [  162.889554][ T3100]  __slab_alloc+0x43/0x70
> [  162.908430][ T3100]  kmem_cache_alloc_trace+0x2f1/0x470
> [  162.932036][ T3100]  iommu_insert_resv_region+0xeb/0x520
> [  162.956179][ T3100]  iommu_get_group_resv_regions+0x16d/0x2f0
> [  162.982083][ T3100]  iommu_group_show_resv_regions+0x8d/0x1f0
> [  163.008373][ T3100]  iommu_group_attr_show+0x34/0x50
> [  163.030557][ T3100]  sysfs_kf_seq_show+0x11c/0x220
> [  163.052038][ T3100]  kernfs_seq_show+0xa4/0xb0
> [  163.072179][ T3100] page last free stack trace:
> [  163.092612][ T3100]  __free_pages_ok+0xa3e/0xb20
> [  163.113361][ T3100]  __free_pages+0x94/0xd0
> [  163.132198][ T3100]  __free_slab+0x177/0x520
> [  163.150922][ T3100]  discard_slab+0x41/0x80
> [  163.169708][ T3100]  __slab_free+0x4b7/0x520
> [  163.188856][ T3100]  ___cache_free+0xc3/0x120
> [  163.208452][ T3100]  qlist_free_all+0x44/0xa0
> [  163.228335][ T3100]  quarantine_reduce+0x1b0/0x240
> [  163.253120][ T3100]  __kasan_kmalloc.constprop.13+0x98/0xd0
> [  163.279865][ T3100]  kasan_slab_alloc+0x11/0x20
> [  163.300175][ T3100]  kmem_cache_alloc+0x17a/0x450
> [  163.321373][ T3100]  ptlock_alloc+0x20/0x50
> [  163.340168][ T3100]  pte_alloc_one+0x40/0xf0
> [  163.359310][ T3100]  __handle_mm_fault+0x1257/0x1300
> [  163.381603][ T3100]  handle_mm_fault+0x205/0x4c0
> [  163.402312][ T3100]  __do_page_fault+0x29c/0x640
> [  163.423082][ T3100] 
> [  163.432556][ T3100] Memory state around the buggy address:
> [  163.457292][ T3100]  ffff8887aba78300: fc fc fc fc fc fc fc fc fc fc fc fc fc
> fc fc fc
> [  163.492994][ T3100]  ffff8887aba78380: fc fc fc fc fc fc fc fc fc fc fc fc fc
> fc fc fc
> [  163.528530][ T3100] >ffff8887aba78400: fc fc fc fc fc fc fc fc fb fb fb fb fb
> fb fb fb
> [  163.565023][ T3100]                                                        ^
> [  163.598027][ T3100]  ffff8887aba78480: fc fc fc fc fc fc fc fc fc fc fc fc fc
> fc fc fc
> [  163.633747][ T3100]  ffff8887aba78500: fc fc fc fc fc fc fc fc fc fc fc fc fc
> fc fc fc
> [  163.669828][ T3100]
> ==================================================================
> [  163.705417][ T3100] Disabling lock debugging due to kernel taint
> 

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