Re: [syzbot] UBSAN: array-index-out-of-bounds in truncate_inode_pages_range

Re: [syzbot] UBSAN: array-index-out-of-bounds in truncate_inode_pages_range

[Andrew Morton]

On Wed, 31 Aug 2022 17:13:36 -0700 syzbot <syzbot+5867885efe39089b339b@syzkaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    89b749d8552d Merge tag 'fbdev-for-6.0-rc3' of git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14b9661b080000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=911efaff115942bb
> dashboard link: https://syzkaller.appspot.com/bug?extid=5867885efe39089b339b
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: i386
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+5867885efe39089b339b@syzkaller.appspotmail.com
> 
> ntfs3: loop0: Different NTFS' sector size (1024) and media sector size (512)
> ntfs3: loop0: RAW NTFS volume: Filesystem size 0.00 Gb > volume size 0.00 Gb. Mount in read-only
> ================================================================================
> UBSAN: array-index-out-of-bounds in mm/truncate.c:366:18
> index 254 is out of range for type 'long unsigned int [15]'

That's

		index = indices[folio_batch_count(&fbatch) - 1] + 1;

I looked.  I see no way in which fbatch.nr got a value of 255.


I must say, the the code looks rather hacky.  Isn't there a more
type-friendly way of doing this?

Re: [syzbot] UBSAN: array-index-out-of-bounds in truncate_inode_pages_range

[Dmitry Vyukov]

On Fri, 2 Sept 2022 at 01:25, Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed, 31 Aug 2022 17:13:36 -0700 syzbot <syzbot+5867885efe39089b339b@syzkaller.appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    89b749d8552d Merge tag 'fbdev-for-6.0-rc3' of git://git.ke..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=14b9661b080000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=911efaff115942bb
> > dashboard link: https://syzkaller.appspot.com/bug?extid=5867885efe39089b339b
> > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > userspace arch: i386
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+5867885efe39089b339b@syzkaller.appspotmail.com
> >
> > ntfs3: loop0: Different NTFS' sector size (1024) and media sector size (512)
> > ntfs3: loop0: RAW NTFS volume: Filesystem size 0.00 Gb > volume size 0.00 Gb. Mount in read-only
> > ================================================================================
> > UBSAN: array-index-out-of-bounds in mm/truncate.c:366:18
> > index 254 is out of range for type 'long unsigned int [15]'
>
> That's
>
>                 index = indices[folio_batch_count(&fbatch) - 1] + 1;
>
> I looked.  I see no way in which fbatch.nr got a value of 255.
>
>
> I must say, the the code looks rather hacky.  Isn't there a more
> type-friendly way of doing this?

I don't see how this can happen either. Also can't reproduce.
It's happened only once so far, so maybe some silent memory corruption.
Let's wait for more crashes/reproducer, or otherwise syzbot will
auto-close it after some time.

Re: [syzbot] UBSAN: array-index-out-of-bounds in truncate_inode_pages_range

[Matthew Wilcox]

On Thu, Sep 01, 2022 at 04:24:59PM -0700, Andrew Morton wrote:
> On Wed, 31 Aug 2022 17:13:36 -0700 syzbot <syzbot+5867885efe39089b339b@syzkaller.appspotmail.com> wrote:
> 
> > Hello,
> > 
> > syzbot found the following issue on:
> > 
> > HEAD commit:    89b749d8552d Merge tag 'fbdev-for-6.0-rc3' of git://git.ke..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=14b9661b080000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=911efaff115942bb
> > dashboard link: https://syzkaller.appspot.com/bug?extid=5867885efe39089b339b
> > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > userspace arch: i386
> > 
> > Unfortunately, I don't have any reproducer for this issue yet.
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+5867885efe39089b339b@syzkaller.appspotmail.com
> > 
> > ntfs3: loop0: Different NTFS' sector size (1024) and media sector size (512)
> > ntfs3: loop0: RAW NTFS volume: Filesystem size 0.00 Gb > volume size 0.00 Gb. Mount in read-only
> > ================================================================================
> > UBSAN: array-index-out-of-bounds in mm/truncate.c:366:18
> > index 254 is out of range for type 'long unsigned int [15]'
> 
> That's
> 
> 		index = indices[folio_batch_count(&fbatch) - 1] + 1;
> 
> I looked.  I see no way in which fbatch.nr got a value of 255.

NTFS is involved.  I stopped looking at that point; it seems to be
riddled with buffer overflows.

> I must say, the the code looks rather hacky.  Isn't there a more
> type-friendly way of doing this?

Looking at the three callers, they all want to advance index.  We
should probably pass &index instead of index and have find_lock_entries
advance it for them.

Vishal, want to take this on?

Re: [syzbot] UBSAN: array-index-out-of-bounds in truncate_inode_pages_range

[Vishal Moola]

On Sat, Oct 8, 2022 at 12:12 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Thu, Sep 01, 2022 at 04:24:59PM -0700, Andrew Morton wrote:
> > On Wed, 31 Aug 2022 17:13:36 -0700 syzbot <syzbot+5867885efe39089b339b@syzkaller.appspotmail.com> wrote:
> >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit:    89b749d8552d Merge tag 'fbdev-for-6.0-rc3' of git://git.ke..
> > > git tree:       upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=14b9661b080000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=911efaff115942bb
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=5867885efe39089b339b
> > > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > userspace arch: i386
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+5867885efe39089b339b@syzkaller.appspotmail.com
> > >
> > > ntfs3: loop0: Different NTFS' sector size (1024) and media sector size (512)
> > > ntfs3: loop0: RAW NTFS volume: Filesystem size 0.00 Gb > volume size 0.00 Gb. Mount in read-only
> > > ================================================================================
> > > UBSAN: array-index-out-of-bounds in mm/truncate.c:366:18
> > > index 254 is out of range for type 'long unsigned int [15]'
> >
> > That's
> >
> >               index = indices[folio_batch_count(&fbatch) - 1] + 1;
> >
> > I looked.  I see no way in which fbatch.nr got a value of 255.
>
> NTFS is involved.  I stopped looking at that point; it seems to be
> riddled with buffer overflows.
>
> > I must say, the the code looks rather hacky.  Isn't there a more
> > type-friendly way of doing this?
>
> Looking at the three callers, they all want to advance index.  We
> should probably pass &index instead of index and have find_lock_entries
> advance it for them.
>
> Vishal, want to take this on?

Yup! I'll do that.

Re: [syzbot] UBSAN: array-index-out-of-bounds in truncate_inode_pages_range

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    e8bc52cb8df8 Merge tag 'driver-core-6.1-rc1' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11a70a42880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7579993da6496f03
dashboard link: https://syzkaller.appspot.com/bug?extid=5867885efe39089b339b
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=153137b8880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=123cae34880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4dc25a89bfbd/disk-e8bc52cb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/16c9ca5fd754/vmlinux-e8bc52cb.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/f3507911193f/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5867885efe39089b339b@syzkaller.appspotmail.com

ntfs3: loop0: Different NTFS' sector size (1024) and media sector size (512)
==================================================================
BUG: KASAN: out-of-bounds in folio_batch_count include/linux/pagevec.h:108 [inline]
BUG: KASAN: out-of-bounds in truncate_inode_pages_range+0x512/0x17b0 mm/truncate.c:366
Read of size 1 at addr ffffc9000b40f8a0 by task syz-executor300/12162

CPU: 1 PID: 12162 Comm: syz-executor300 Not tainted 6.0.0-syzkaller-07994-ge8bc52cb8df8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 print_address_description+0x65/0x4b0 mm/kasan/report.c:317
 print_report+0x108/0x220 mm/kasan/report.c:433
 kasan_report+0xfb/0x130 mm/kasan/report.c:495
 folio_batch_count include/linux/pagevec.h:108 [inline]
 truncate_inode_pages_range+0x512/0x17b0 mm/truncate.c:366
 ntfs_evict_inode+0x18/0xb0 fs/ntfs3/inode.c:1741
 evict+0x2a4/0x620 fs/inode.c:664
 ntfs_fill_super+0x3c6c/0x4420 fs/ntfs3/super.c:1190
 get_tree_bdev+0x400/0x620 fs/super.c:1323
 vfs_get_tree+0x88/0x270 fs/super.c:1530
 do_new_mount+0x289/0xad0 fs/namespace.c:3040
 do_mount fs/namespace.c:3383 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3568
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f1170f482fa
Code: 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 a8 00 00 00 0f 1f 84 00 00 00 00 00 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:00007f1170eee168 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f1170f482fa
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f1170eee180
RBP: 0000000000000004 R08: 00007f1170eee1c0 R09: 00007f1170eee6b8
R10: 0000000000000000 R11: 0000000000000286 R12: 00007f1170eee1c0
R13: 0000000000000110 R14: 00007f1170eee180 R15: 0000000020001b80
 </TASK>

The buggy address belongs to stack of task syz-executor300/12162
 and is located at offset 32 in frame:
 truncate_inode_pages_range+0x0/0x17b0

This frame has 2 objects:
 [32, 160) 'fbatch'
 [192, 312) 'indices'

The buggy address belongs to the virtual mapping at
 [ffffc9000b408000, ffffc9000b411000) created by:
 dup_task_struct+0x8b/0x490 kernel/fork.c:977

The buggy address belongs to the physical page:
page:ffffea0001d7b300 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x75ecc
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 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 12161, tgid 12161 (syz-executor300), ts 362387697256, free_ts 362353989799
 prep_new_page mm/page_alloc.c:2532 [inline]
 get_page_from_freelist+0x72b/0x7a0 mm/page_alloc.c:4283
 __alloc_pages+0x259/0x560 mm/page_alloc.c:5549
 vm_area_alloc_pages mm/vmalloc.c:2958 [inline]
 __vmalloc_area_node mm/vmalloc.c:3026 [inline]
 __vmalloc_node_range+0x8f4/0x1290 mm/vmalloc.c:3196
 alloc_thread_stack_node+0x307/0x500 kernel/fork.c:312
 dup_task_struct+0x8b/0x490 kernel/fork.c:977
 copy_process+0x637/0x3f60 kernel/fork.c:2085
 kernel_clone+0x22f/0x7a0 kernel/fork.c:2671
 __do_sys_clone kernel/fork.c:2805 [inline]
 __se_sys_clone kernel/fork.c:2789 [inline]
 __x64_sys_clone+0x276/0x2e0 kernel/fork.c:2789
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 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:1449 [inline]
 free_pcp_prepare+0x812/0x900 mm/page_alloc.c:1499
 free_unref_page_prepare mm/page_alloc.c:3380 [inline]
 free_unref_page+0x7d/0x630 mm/page_alloc.c:3476
 mm_free_pgd kernel/fork.c:737 [inline]
 __mmdrop+0xae/0x3f0 kernel/fork.c:788
 exit_mm+0x211/0x2f0 kernel/exit.c:510
 do_exit+0x4e1/0x20a0 kernel/exit.c:782
 do_group_exit+0x23b/0x2f0 kernel/exit.c:925
 get_signal+0x172f/0x1780 kernel/signal.c:2857
 arch_do_signal_or_restart+0x8d/0x750 arch/x86/kernel/signal.c:869
 exit_to_user_mode_loop+0x74/0x160 kernel/entry/common.c:166
 exit_to_user_mode_prepare+0xad/0x110 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x2e/0x60 kernel/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Memory state around the buggy address:
 ffffc9000b40f780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc9000b40f800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc9000b40f880: f1 f1 f1 f1 00 00 00 00 00 00 00 00 00 00 00 00
                                  ^
 ffffc9000b40f900: 00 00 00 00 f2 f2 f2 f2 00 00 00 00 00 00 00 00
 ffffc9000b40f980: 00 00 00 00 00 00 00 f3 f3 f3 f3 f3 00 00 00 00
==================================================================