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Date:   Wed, 27 Apr 2022 14:55:58 +0200
From:   Christian Brauner <brauner@kernel.org>
To:     syzbot <syzbot+7170d66493145b71afd4@syzkaller.appspotmail.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk,
        Matthew Wilcox <willy@infradead.org>
Subject: Re: [syzbot] KASAN: use-after-free Read in mas_next_nentry
Message-ID: <20220427125558.5cx4iv3mgjqi36ld@wittgenstein>
References: <0000000000009ecbf205dda227bd@google.com>
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[+Cc Willy]

On Wed, Apr 27, 2022 at 05:43:22AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    f02ac5c95dfd Add linux-next specific files for 20220427
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=14bd8db2f00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e9256c70f586da8a
> dashboard link: https://syzkaller.appspot.com/bug?extid=7170d66493145b71afd4
> 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=113b4252f00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1174bcbaf00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+7170d66493145b71afd4@syzkaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: use-after-free in mas_safe_min lib/maple_tree.c:715 [inline]
> BUG: KASAN: use-after-free in mas_next_nentry+0x997/0xaa0 lib/maple_tree.c:4546
> Read of size 8 at addr ffff88807811e418 by task syz-executor361/3593
> 
> CPU: 1 PID: 3593 Comm: syz-executor361 Not tainted 5.18.0-rc4-next-20220427-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>  print_address_description.constprop.0.cold+0xeb/0x495 mm/kasan/report.c:313
>  print_report mm/kasan/report.c:429 [inline]
>  kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491
>  mas_safe_min lib/maple_tree.c:715 [inline]
>  mas_next_nentry+0x997/0xaa0 lib/maple_tree.c:4546
>  mas_next_entry lib/maple_tree.c:4636 [inline]
>  mas_next+0x1eb/0xc40 lib/maple_tree.c:5723
>  userfaultfd_register fs/userfaultfd.c:1468 [inline]
>  userfaultfd_ioctl+0x2527/0x40f0 fs/userfaultfd.c:1993
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:870 [inline]
>  __se_sys_ioctl fs/ioctl.c:856 [inline]
>  __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7f4e5785d939
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 91 18 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 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:00007ffff7501a18 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000031 RCX: 00007f4e5785d939
> RDX: 00000000200001c0 RSI: 00000000c020aa00 RDI: 0000000000000003
> RBP: 00007ffff7501b10 R08: 00007ffff7501a72 R09: 00007ffff7501a72
> R10: 00007ffff7501a72 R11: 0000000000000246 R12: 00007ffff7501ae0
> R13: 00007f4e578e14e0 R14: 0000000000000003 R15: 00007ffff7501a72
>  </TASK>
> 
> Allocated by task 3592:
>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
>  kasan_set_track mm/kasan/common.c:45 [inline]
>  set_alloc_info mm/kasan/common.c:436 [inline]
>  __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
>  kasan_slab_alloc include/linux/kasan.h:224 [inline]
>  slab_post_alloc_hook mm/slab.h:750 [inline]
>  kmem_cache_alloc_bulk+0x39f/0x720 mm/slub.c:3728
>  mt_alloc_bulk lib/maple_tree.c:151 [inline]
>  mas_alloc_nodes+0x1df/0x6b0 lib/maple_tree.c:1244
>  mas_node_count+0x101/0x130 lib/maple_tree.c:1303
>  mas_split lib/maple_tree.c:3406 [inline]
>  mas_commit_b_node lib/maple_tree.c:3508 [inline]
>  mas_wr_modify+0x2505/0x5ac0 lib/maple_tree.c:4251
>  mas_wr_store_entry.isra.0+0x66e/0x10f0 lib/maple_tree.c:4289
>  mas_store+0xac/0xf0 lib/maple_tree.c:5523
>  dup_mmap+0x845/0x1030 kernel/fork.c:687
>  dup_mm+0x91/0x370 kernel/fork.c:1516
>  copy_mm kernel/fork.c:1565 [inline]
>  copy_process+0x3b07/0x6fd0 kernel/fork.c:2226
>  kernel_clone+0xe7/0xab0 kernel/fork.c:2631
>  __do_sys_clone+0xc8/0x110 kernel/fork.c:2748
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Freed by task 3593:
>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
>  kasan_set_track+0x21/0x30 mm/kasan/common.c:45
>  kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
>  ____kasan_slab_free mm/kasan/common.c:366 [inline]
>  ____kasan_slab_free+0x166/0x1a0 mm/kasan/common.c:328
>  kasan_slab_free include/linux/kasan.h:200 [inline]
>  slab_free_hook mm/slub.c:1727 [inline]
>  slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1753
>  slab_free mm/slub.c:3507 [inline]
>  kmem_cache_free_bulk mm/slub.c:3654 [inline]
>  kmem_cache_free_bulk+0x2c0/0xb60 mm/slub.c:3641
>  mt_free_bulk lib/maple_tree.c:157 [inline]
>  mas_destroy+0x394/0x5c0 lib/maple_tree.c:5685
>  mas_store_prealloc+0xec/0x150 lib/maple_tree.c:5567
>  vma_mas_store mm/internal.h:482 [inline]
>  __vma_adjust+0x6ba/0x18f0 mm/mmap.c:811
>  vma_adjust include/linux/mm.h:2654 [inline]
>  __split_vma+0x443/0x530 mm/mmap.c:2259
>  split_vma+0x9f/0xe0 mm/mmap.c:2292
>  userfaultfd_register fs/userfaultfd.c:1444 [inline]
>  userfaultfd_ioctl+0x39f4/0x40f0 fs/userfaultfd.c:1993
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:870 [inline]
>  __se_sys_ioctl fs/ioctl.c:856 [inline]
>  __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> The buggy address belongs to the object at ffff88807811e400
>  which belongs to the cache maple_node of size 256
> The buggy address is located 24 bytes inside of
>  256-byte region [ffff88807811e400, ffff88807811e500)
> 
> The buggy address belongs to the physical page:
> page:ffffea0001e04780 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7811e
> head:ffffea0001e04780 order:1 compound_mapcount:0 compound_pincount:0
> flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000010200 0000000000000000 dead000000000001 ffff888010c4fdc0
> raw: 0000000000000000 0000000000100010 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 3286, tgid 3286 (dhcpcd-run-hook), ts 27966983290, free_ts 22717162691
>  prep_new_page mm/page_alloc.c:2431 [inline]
>  get_page_from_freelist+0xba2/0x3e00 mm/page_alloc.c:4172
>  __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5393
>  alloc_pages+0x1aa/0x310 mm/mempolicy.c:2281
>  alloc_slab_page mm/slub.c:1797 [inline]
>  allocate_slab+0x26c/0x3c0 mm/slub.c:1942
>  new_slab mm/slub.c:2002 [inline]
>  ___slab_alloc+0x985/0xd90 mm/slub.c:3002
>  kmem_cache_alloc_bulk+0x21c/0x720 mm/slub.c:3704
>  mt_alloc_bulk lib/maple_tree.c:151 [inline]
>  mas_alloc_nodes+0x2b0/0x6b0 lib/maple_tree.c:1244
>  mas_preallocate+0xfb/0x270 lib/maple_tree.c:5581
>  __vma_adjust+0x226/0x18f0 mm/mmap.c:742
>  vma_adjust include/linux/mm.h:2654 [inline]
>  __split_vma+0x443/0x530 mm/mmap.c:2259
>  do_mas_align_munmap+0x4f5/0xe80 mm/mmap.c:2375
>  do_mas_munmap+0x202/0x2c0 mm/mmap.c:2499
>  mmap_region+0x219/0x1c70 mm/mmap.c:2547
>  do_mmap+0x825/0xf60 mm/mmap.c:1471
>  vm_mmap_pgoff+0x1b7/0x290 mm/util.c:488
>  ksys_mmap_pgoff+0x40d/0x5a0 mm/mmap.c:1517
> page last free stack trace:
>  reset_page_owner include/linux/page_owner.h:24 [inline]
>  free_pages_prepare mm/page_alloc.c:1346 [inline]
>  free_pcp_prepare+0x549/0xd20 mm/page_alloc.c:1396
>  free_unref_page_prepare mm/page_alloc.c:3318 [inline]
>  free_unref_page+0x19/0x6a0 mm/page_alloc.c:3413
>  __unfreeze_partials+0x17c/0x1a0 mm/slub.c:2521
>  qlink_free mm/kasan/quarantine.c:168 [inline]
>  qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187
>  kasan_quarantine_reduce+0x180/0x200 mm/kasan/quarantine.c:294
>  __kasan_slab_alloc+0xa2/0xc0 mm/kasan/common.c:446
>  kasan_slab_alloc include/linux/kasan.h:224 [inline]
>  slab_post_alloc_hook mm/slab.h:750 [inline]
>  slab_alloc_node mm/slub.c:3214 [inline]
>  slab_alloc mm/slub.c:3222 [inline]
>  __kmalloc+0x200/0x350 mm/slub.c:4415
>  kmalloc include/linux/slab.h:593 [inline]
>  tomoyo_realpath_from_path+0xc3/0x620 security/tomoyo/realpath.c:254
>  tomoyo_realpath_nofollow+0xc8/0xe0 security/tomoyo/realpath.c:309
>  tomoyo_find_next_domain+0x280/0x1f80 security/tomoyo/domain.c:727
>  tomoyo_bprm_check_security security/tomoyo/tomoyo.c:101 [inline]
>  tomoyo_bprm_check_security+0x121/0x1a0 security/tomoyo/tomoyo.c:91
>  security_bprm_check+0x45/0xa0 security/security.c:865
>  search_binary_handler fs/exec.c:1718 [inline]
>  exec_binprm fs/exec.c:1771 [inline]
>  bprm_execve fs/exec.c:1840 [inline]
>  bprm_execve+0x732/0x1970 fs/exec.c:1802
>  do_execveat_common+0x727/0x890 fs/exec.c:1945
>  do_execve fs/exec.c:2015 [inline]
>  __do_sys_execve fs/exec.c:2091 [inline]
>  __se_sys_execve fs/exec.c:2086 [inline]
>  __x64_sys_execve+0x8f/0xc0 fs/exec.c:2086
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> 
> Memory state around the buggy address:
>  ffff88807811e300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff88807811e380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >ffff88807811e400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                             ^
>  ffff88807811e480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff88807811e500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
> 
> 
> ---
> 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@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches