Re: [syzbot] [mm?] KASAN: slab-out-of-bounds Read in mt_validate_nulls

[Liam R. Howlett]

#syz fix: mm: validate the mm before dropping the mmap lock

* syzbot <syzbot+609e63261638ff3d5436@xxxxxxxxxxxxxxxxxxxxxxxxx> [230705 21:23]:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    a901a3568fd2 Merge tag 'iomap-6.5-merge-1' of git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=116a6d68a80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=7406f415f386e786
> dashboard link: https://syzkaller.appspot.com/bug?extid=609e63261638ff3d5436
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10342968a80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17d4cf70a80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/119fd918f733/disk-a901a356.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/79f9ac119639/vmlinux-a901a356.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/8bd8662e2869/bzImage-a901a356.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/183577244af6/mount_0.gz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+609e63261638ff3d5436@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> R10: 0000000000002000 R11: 0000000000000246 R12: 00007fb71e6c96b8
> R13: 00007fb71e6c9180 R14: 00007fb71e6c91c0 R15: 00007fb71e7a16e8
>  </TASK>
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in mt_slot lib/maple_tree.c:816 [inline]
> BUG: KASAN: slab-out-of-bounds in mas_slot lib/maple_tree.c:849 [inline]
> BUG: KASAN: slab-out-of-bounds in mt_validate_nulls+0xc04/0xd10 lib/maple_tree.c:7172
> Read of size 8 at addr ffff8880770ab100 by task syz-executor263/7002
> 
> CPU: 0 PID: 7002 Comm: syz-executor263 Not tainted 6.4.0-syzkaller-10173-ga901a3568fd2 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
>  print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:364
>  print_report mm/kasan/report.c:475 [inline]
>  kasan_report+0x11d/0x130 mm/kasan/report.c:588
>  mt_slot lib/maple_tree.c:816 [inline]
>  mas_slot lib/maple_tree.c:849 [inline]
>  mt_validate_nulls+0xc04/0xd10 lib/maple_tree.c:7172
>  mt_validate+0x17e3/0x4370 lib/maple_tree.c:7227
>  validate_mm+0x9d/0x470 mm/mmap.c:300
>  do_vmi_align_munmap+0x1199/0x1680 mm/mmap.c:2561
>  do_vmi_munmap+0x266/0x430 mm/mmap.c:2619
>  __vm_munmap+0x137/0x380 mm/mmap.c:2899
>  __do_sys_munmap mm/mmap.c:2916 [inline]
>  __se_sys_munmap mm/mmap.c:2913 [inline]
>  __x64_sys_munmap+0x62/0x80 mm/mmap.c:2913
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7fb71e71cef7
> Code: 00 00 00 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb 85 66 2e 0f 1f 84 00 00 00 00 00 90 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fb71e6c9168 EFLAGS: 00000246 ORIG_RAX: 000000000000000b
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fb71e71cef7
> RDX: 0000000000002000 RSI: 0000000000002000 RDI: 00007fb716288000
> RBP: 00007fb716288000 R08: 0000000000000000 R09: 0000000000000176
> R10: 0000000000002000 R11: 0000000000000246 R12: 00007fb71e6c96b8
> R13: 00007fb71e6c9180 R14: 00007fb71e6c91c0 R15: 00007fb71e7a16e8
>  </TASK>
> 
> Allocated by task 7002:
>  kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
>  kasan_set_track+0x25/0x30 mm/kasan/common.c:52
>  __kasan_slab_alloc+0x7f/0x90 mm/kasan/common.c:328
>  kasan_slab_alloc include/linux/kasan.h:186 [inline]
>  slab_post_alloc_hook mm/slab.h:750 [inline]
>  slab_alloc_node mm/slub.c:3470 [inline]
>  slab_alloc mm/slub.c:3478 [inline]
>  __kmem_cache_alloc_lru mm/slub.c:3485 [inline]
>  kmem_cache_alloc+0x16c/0x380 mm/slub.c:3494
>  mt_alloc_one lib/maple_tree.c:159 [inline]
>  mas_alloc_nodes+0x4ec/0x8b0 lib/maple_tree.c:1282
>  mas_node_count_gfp+0x106/0x140 lib/maple_tree.c:1362
>  mas_node_count lib/maple_tree.c:1376 [inline]
>  mas_wr_node_store+0xa64/0x1170 lib/maple_tree.c:4100
>  mas_wr_modify+0x28b/0x10d0 lib/maple_tree.c:4346
>  mas_wr_store_entry.isra.0+0x495/0x1030 lib/maple_tree.c:4390
>  mas_store_gfp+0xce/0x1f0 lib/maple_tree.c:5506
>  vma_iter_clear_gfp mm/mmap.c:162 [inline]
>  do_vmi_align_munmap+0xd02/0x1680 mm/mmap.c:2538
>  do_vmi_munmap+0x266/0x430 mm/mmap.c:2619
>  __vm_munmap+0x137/0x380 mm/mmap.c:2899
>  __do_sys_munmap mm/mmap.c:2916 [inline]
>  __se_sys_munmap mm/mmap.c:2913 [inline]
>  __x64_sys_munmap+0x62/0x80 mm/mmap.c:2913
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Last potentially related work creation:
>  kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
>  __kasan_record_aux_stack+0xb9/0xd0 mm/kasan/generic.c:491
>  __call_rcu_common.constprop.0+0x99/0x7e0 kernel/rcu/tree.c:2649
>  ma_free_rcu lib/maple_tree.c:189 [inline]
>  mas_free lib/maple_tree.c:1344 [inline]
>  mas_replace+0x98c/0xfa0 lib/maple_tree.c:1785
>  mas_wr_node_store+0xcab/0x1170 lib/maple_tree.c:4151
>  mas_wr_modify+0x28b/0x10d0 lib/maple_tree.c:4346
>  mas_wr_store_entry.isra.0+0x495/0x1030 lib/maple_tree.c:4390
>  mas_store_prealloc+0xb3/0x270 lib/maple_tree.c:5529
>  mmap_region+0x91c/0x2570 mm/mmap.c:2811
>  do_mmap+0x850/0xee0 mm/mmap.c:1362
>  vm_mmap_pgoff+0x1a2/0x3b0 mm/util.c:543
>  ksys_mmap_pgoff+0x7d/0x5b0 mm/mmap.c:1408
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Second to last potentially related work creation:
>  kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
>  __kasan_record_aux_stack+0xb9/0xd0 mm/kasan/generic.c:491
>  __call_rcu_common.constprop.0+0x99/0x7e0 kernel/rcu/tree.c:2649
>  ma_free_rcu lib/maple_tree.c:189 [inline]
>  mas_free lib/maple_tree.c:1344 [inline]
>  mas_replace+0x98c/0xfa0 lib/maple_tree.c:1785
>  mas_wr_node_store+0xcab/0x1170 lib/maple_tree.c:4151
>  mas_wr_modify+0x28b/0x10d0 lib/maple_tree.c:4346
>  mas_wr_store_entry.isra.0+0x495/0x1030 lib/maple_tree.c:4390
>  mas_store_prealloc+0xb3/0x270 lib/maple_tree.c:5529
>  vma_complete+0x8fd/0xdc0 mm/mmap.c:553
>  __split_vma+0x53b/0x830 mm/mmap.c:2381
>  split_vma+0xc6/0x110 mm/mmap.c:2409
>  mprotect_fixup+0x891/0xbd0 mm/mprotect.c:643
>  do_mprotect_pkey+0x883/0xd40 mm/mprotect.c:817
>  __do_sys_mprotect mm/mprotect.c:838 [inline]
>  __se_sys_mprotect mm/mprotect.c:835 [inline]
>  __x64_sys_mprotect+0x78/0xb0 mm/mprotect.c:835
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> The buggy address belongs to the object at ffff8880770ab000
>  which belongs to the cache maple_node of size 256
> The buggy address is located 0 bytes to the right of
>  allocated 256-byte region [ffff8880770ab000, ffff8880770ab100)
> 
> The buggy address belongs to the physical page:
> page:ffffea0001dc2a80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x770aa
> head:ffffea0001dc2a80 order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> anon flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
> page_type: 0xffffffff()
> raw: 00fff00000010200 ffff88801324d000 0000000000000000 dead000000000001
> raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 1, migratetype Unmovable, gfp_mask 0x52800(GFP_NOWAIT|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 4689, tgid 4689 (dhcpcd-run-hook), ts 21566309288, free_ts 20023594773
>  set_page_owner include/linux/page_owner.h:31 [inline]
>  post_alloc_hook+0x2db/0x350 mm/page_alloc.c:1570
>  prep_new_page mm/page_alloc.c:1577 [inline]
>  get_page_from_freelist+0xfed/0x2d30 mm/page_alloc.c:3221
>  __alloc_pages+0x1cb/0x4a0 mm/page_alloc.c:4477
>  alloc_pages+0x1aa/0x270 mm/mempolicy.c:2279
>  alloc_slab_page mm/slub.c:1862 [inline]
>  allocate_slab+0x25f/0x390 mm/slub.c:2009
>  new_slab mm/slub.c:2062 [inline]
>  ___slab_alloc+0xbc3/0x15d0 mm/slub.c:3215
>  __kmem_cache_alloc_bulk mm/slub.c:3966 [inline]
>  kmem_cache_alloc_bulk+0x270/0x860 mm/slub.c:4041
>  mt_alloc_bulk lib/maple_tree.c:164 [inline]
>  mas_alloc_nodes+0x341/0x8b0 lib/maple_tree.c:1304
>  mas_node_count_gfp+0x106/0x140 lib/maple_tree.c:1362
>  mas_node_count lib/maple_tree.c:1376 [inline]
>  mas_expected_entries+0x117/0x200 lib/maple_tree.c:5656
>  vma_iter_bulk_alloc include/linux/mm.h:898 [inline]
>  dup_mmap+0x4e4/0x19b0 kernel/fork.c:681
>  dup_mm kernel/fork.c:1688 [inline]
>  copy_mm kernel/fork.c:1737 [inline]
>  copy_process+0x6663/0x75c0 kernel/fork.c:2503
>  kernel_clone+0xeb/0x890 kernel/fork.c:2911
>  __do_sys_clone+0xba/0x100 kernel/fork.c:3054
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> page last free stack trace:
>  reset_page_owner include/linux/page_owner.h:24 [inline]
>  free_pages_prepare mm/page_alloc.c:1161 [inline]
>  free_unref_page_prepare+0x62e/0xcb0 mm/page_alloc.c:2348
>  free_unref_page+0x33/0x370 mm/page_alloc.c:2443
>  qlink_free mm/kasan/quarantine.c:166 [inline]
>  qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:185
>  kasan_quarantine_reduce+0x195/0x220 mm/kasan/quarantine.c:292
>  __kasan_slab_alloc+0x63/0x90 mm/kasan/common.c:305
>  kasan_slab_alloc include/linux/kasan.h:186 [inline]
>  slab_post_alloc_hook mm/slab.h:750 [inline]
>  slab_alloc_node mm/slub.c:3470 [inline]
>  slab_alloc mm/slub.c:3478 [inline]
>  __kmem_cache_alloc_lru mm/slub.c:3485 [inline]
>  kmem_cache_alloc+0x16c/0x380 mm/slub.c:3494
>  getname_flags.part.0+0x50/0x4f0 fs/namei.c:140
>  getname_flags+0x9e/0xe0 include/linux/audit.h:319
>  user_path_at_empty+0x2f/0x60 fs/namei.c:2906
>  do_readlinkat+0xcd/0x2f0 fs/stat.c:477
>  __do_sys_readlink fs/stat.c:510 [inline]
>  __se_sys_readlink fs/stat.c:507 [inline]
>  __x64_sys_readlink+0x78/0xb0 fs/stat.c:507
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Memory state around the buggy address:
>  ffff8880770ab000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffff8880770ab080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >ffff8880770ab100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>                    ^
>  ffff8880770ab180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff8880770ab200: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
> 
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> 
> If the bug is already fixed, let syzbot know by replying with:
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> 
> If you want syzbot to run the reproducer, reply with:
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> 
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> 
> If the bug is a duplicate of another bug, reply with:
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> 
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>