Date:   Wed, 20 Jul 2022 17:59:44 -0700
From:   Dipanjan Das <mail.dipanjan.das@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     jlayton@...nel.org, neilb@...e.de,
        damien.lemoal@...nsource.wdc.com, jack@...e.cz,
        reiserfs-devel@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller@...glegroups.com, fleischermarius@...glemail.com,
        its.priyanka.bose@...il.com
Subject: Re: KASAN: vmalloc-out-of-bounds Read in cleanup_bitmap_list

On Sun, Jul 17, 2022 at 4:33 PM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Sun, Jul 17, 2022 at 03:24:33PM -0700, Dipanjan Das wrote:
> > Hi,
> >
> > We would like to report the following bug which has been found by our
> > modified version of syzkaller.
>
> Modified how?

We are from an academic research group. The bugs we are reporting are
the outcome of an academic research project. Since this is a work-in-progress,
which is why, we cannot unfortunately reveal much details at the moment.

> Something you need to understand is that we are
> _drowning_ in syzbot bug reports.  We are not short on bugs to fix, we
> are short on people to fix them.  Having a new source of bug reports
> is just not helpful.

We understand the frustration. We deeply apologize for our last bug report
not being very helpful. We struggled a bit to come up with a syzkaller
reproducer.
Please find it attached. The repro needs to be run like:

./syz-execprog -executor=./syz-executor -repeat=0 -procs=16 -cover=0 repro.syz

Unfortunately, the repro is not "one-shot", it takes 1K-2K executions
(which syz-execprog  will do anyway)
to trigger the bug which takes less than five minutes for us. Please
let us know if/what more we can do
to help the developers root cause/fix the issue.

> If you're generating these bug reports by fuzzing a filesystem image,
> then I can see how it happens.  If it's a normal filesystem image,
> then the code looks fine.

We are not specifically mutating the filesystem image as part of our
modification.
That said, it seems syzkaller's syz_mount_image pseudo syscall already generates
filesystem images on the fly. Therefore, your first suspicion may very
well be correct.

>
> The obvious integer overflow is:
>
>                                    unsigned int bmap_nr)
> ...
>         int mem = bmap_nr * sizeof(struct reiserfs_bitmap_node *);
>
> but I don't even know if that's where to look.
>
> > ======================================================
> > description: KASAN: vmalloc-out-of-bounds Read in cleanup_bitmap_list
> > affected file: fs/reiserfs/journal.c
> > kernel version: 5.19-rc6
> > kernel commit: 32346491ddf24599decca06190ebca03ff9de7f8
> > git tree: upstream
> > kernel config: attached
> > crash reproducer: none
> > ======================================================
> > Crash log:
> >
> > BUG: KASAN: vmalloc-out-of-bounds in
> > cleanup_bitmap_list.isra.0.part.0+0x4a0/0x5e0
> > fs/reiserfs/journal.c:231
> > Read of size 8 at addr ffffc900136dd008 by task syz-executor.2/13172
> >
> > CPU: 0 PID: 13172 Comm: syz-executor.2 Tainted: G           OE
> > 5.19.0-rc6-g2eae0556bb9d #2
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > 1.13.0-1ubuntu1.1 04/01/2014
> > Call Trace:
> >  <TASK>
> >  __dump_stack lib/dump_stack.c:88 [inline]
> >  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> >  print_address_description mm/kasan/report.c:313 [inline]
> >  print_report.cold+0x176/0x659 mm/kasan/report.c:429
> >  kasan_report+0x8a/0x1b0 mm/kasan/report.c:491
> >  cleanup_bitmap_list.isra.0.part.0+0x4a0/0x5e0 fs/reiserfs/journal.c:231
> >  cleanup_bitmap_list fs/reiserfs/journal.c:227 [inline]
> >  free_list_bitmaps+0x68/0x100 fs/reiserfs/journal.c:249
> >  free_journal_ram+0xfc/0x500 fs/reiserfs/journal.c:1887
> >  do_journal_release fs/reiserfs/journal.c:1960 [inline]
> >  journal_release_error+0x72/0x90 fs/reiserfs/journal.c:1978
> >  reiserfs_fill_super+0x114d/0x2f10 fs/reiserfs/super.c:2225
> >  mount_bdev+0x34d/0x410 fs/super.c:1367
> >  legacy_get_tree+0x105/0x220 fs/fs_context.c:610
> >  vfs_get_tree+0x89/0x2f0 fs/super.c:1497
> >  do_new_mount fs/namespace.c:3040 [inline]
> >  path_mount+0x1228/0x1cb0 fs/namespace.c:3370
> >  do_mount+0xf3/0x110 fs/namespace.c:3383
> >  __do_sys_mount fs/namespace.c:3591 [inline]
> >  __se_sys_mount fs/namespace.c:3568 [inline]
> >  __x64_sys_mount+0x18f/0x230 fs/namespace.c:3568
> >  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+0x46/0xb0
> > RIP: 0033:0x7f121408fe8e
> > Code: 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f
> > 84 00 00 00 00 00 90 f3 0f 1e fa 49 89 ca b8 a5 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:00007f121266a9f8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
> > RAX: ffffffffffffffda RBX: 0000000020000200 RCX: 00007f121408fe8e
> > RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f121266aa50
> > RBP: 00007f121266aa90 R08: 00007f121266aa90 R09: 0000000020000000
> > R10: 0000000000000000 R11: 0000000000000206 R12: 0000000020000000
> > R13: 0000000020000100 R14: 00007f121266aa50 R15: 0000000020000040
> >  </TASK>
> >
> > The buggy address belongs to the virtual mapping at
> >  [ffffc900136dd000, ffffc900136df000) created by:
> >  reiserfs_allocate_list_bitmaps+0x54/0x100 fs/reiserfs/journal.c:290
> >
> > The buggy address belongs to the physical page:
> > page:ffffea00054c2700 refcount:1 mapcount:0 mapping:0000000000000000
> > index:0x0 pfn:0x15309c
> > flags: 0x17ff00000000000(node=0|zone=2|lastcpupid=0x7ff)
> > raw: 017ff00000000000 0000000000000000 dead000000000122 0000000000000000
> > raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
> > page dumped because: kasan: bad access detected
> > page_owner tracks the page as allocated
> > page last allocated via order 0, migratetype Unmovable, gfp_mask
> > 0x2dc2(GFP_KERNEL|__GFP_HIGHMEM|__GFP_NOWARN|__GFP_ZERO), pid 13172,
> > tgid 13167 (syz-executor.2), ts 141798727963, free_ts 133661424124
> >  set_page_owner include/linux/page_owner.h:31 [inline]
> >  post_alloc_hook mm/page_alloc.c:2449 [inline]
> >  prep_new_page+0x297/0x330 mm/page_alloc.c:2456
> >  get_page_from_freelist+0x2142/0x3c80 mm/page_alloc.c:4198
> >  __alloc_pages+0x321/0x710 mm/page_alloc.c:5426
> >  __alloc_pages_bulk+0x974/0x1590 mm/page_alloc.c:5374
> >  alloc_pages_bulk_array_mempolicy+0x12d/0x430 mm/mempolicy.c:2367
> >  vm_area_alloc_pages mm/vmalloc.c:2899 [inline]
> >  __vmalloc_area_node mm/vmalloc.c:2995 [inline]
> >  __vmalloc_node_range+0x52f/0x1360 mm/vmalloc.c:3165
> >  __vmalloc_node mm/vmalloc.c:3230 [inline]
> >  vzalloc+0x67/0x80 mm/vmalloc.c:3303
> >  reiserfs_allocate_list_bitmaps+0x54/0x100 fs/reiserfs/journal.c:290
> >  journal_init+0x3ca/0x64d0 fs/reiserfs/journal.c:2732
> >  reiserfs_fill_super+0xbbb/0x2f10 fs/reiserfs/super.c:2024
> >  mount_bdev+0x34d/0x410 fs/super.c:1367
> >  legacy_get_tree+0x105/0x220 fs/fs_context.c:610
> >  vfs_get_tree+0x89/0x2f0 fs/super.c:1497
> >  do_new_mount fs/namespace.c:3040 [inline]
> >  path_mount+0x1228/0x1cb0 fs/namespace.c:3370
> >  do_mount+0xf3/0x110 fs/namespace.c:3383
> >  __do_sys_mount fs/namespace.c:3591 [inline]
> >  __se_sys_mount fs/namespace.c:3568 [inline]
> >  __x64_sys_mount+0x18f/0x230 fs/namespace.c:3568
> > page last free stack trace:
> >  reset_page_owner include/linux/page_owner.h:24 [inline]
> >  free_pages_prepare mm/page_alloc.c:1371 [inline]
> >  free_pcp_prepare+0x51f/0xd00 mm/page_alloc.c:1421
> >  free_unref_page_prepare mm/page_alloc.c:3343 [inline]
> >  free_unref_page+0x19/0x5b0 mm/page_alloc.c:3438
> >  kasan_depopulate_vmalloc_pte+0x5c/0x70 mm/kasan/shadow.c:359
> >  apply_to_pte_range mm/memory.c:2625 [inline]
> >  apply_to_pmd_range mm/memory.c:2669 [inline]
> >  apply_to_pud_range mm/memory.c:2705 [inline]
> >  apply_to_p4d_range mm/memory.c:2741 [inline]
> >  __apply_to_page_range+0x66e/0xf50 mm/memory.c:2775
> >  kasan_release_vmalloc+0xa2/0xb0 mm/kasan/shadow.c:469
> >  __purge_vmap_area_lazy+0x8fe/0x1c90 mm/vmalloc.c:1722
> >  drain_vmap_area_work+0x52/0xe0 mm/vmalloc.c:1751
> >  process_one_work+0x9cc/0x1650 kernel/workqueue.c:2289
> >  worker_thread+0x623/0x1070 kernel/workqueue.c:2436
> >  kthread+0x2e9/0x3a0 kernel/kthread.c:376
> >  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302
> >
> > Memory state around the buggy address:
> >  ffffc900136dcf00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
> >  ffffc900136dcf80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
> > >ffffc900136dd000: 00 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
> >                       ^
> >  ffffc900136dd080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
> >  ffffc900136dd100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
> > ==================================================================
> >
> > --
> > Thanks & Regards,
> >
> > Dipanjan
>
>

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