[syzbot] [mm?] kernel BUG in __page_table_check_zero (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 850925a8133c Merge tag '9p-for-6.12-rc5' of https://github..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1346c940580000
kernel config: https://syzkaller.appspot.com/x/.config?x=309bb816d40abc28
dashboard link: https://syzkaller.appspot.com/bug?extid=ccc0e1cfdb72b664f0d8
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=158ab65f980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=120e6a87980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/da8019730dec/disk-850925a8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b1ee80babbbc/vmlinux-850925a8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/462580e2ad54/bzImage-850925a8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ccc0e1...@syzkaller.appspotmail.com

Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 a1 1a 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:00007ffede422258 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007ffede422280 RCX: 00007f69e1b3c569
RDX: 0000000002000005 RSI: 0000000000003000 RDI: 000000002001a000
RBP: 0000000000000001 R08: 0000000000000003 R09: 0000000080000000
R10: 0000000000011012 R11: 0000000000000246 R12: 00007ffede42227c
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
</TASK>
------------[ cut here ]------------
kernel BUG at mm/page_table_check.c:157!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
CPU: 1 UID: 0 PID: 5850 Comm: syz-executor279 Not tainted 6.12.0-rc4-syzkaller-00261-g850925a8133c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:__page_table_check_zero+0x274/0x350 mm/page_table_check.c:157
Code: c1 0f 8c 39 fe ff ff 48 89 df e8 87 28 f3 ff e9 2c fe ff ff e8 dd 6a 89 ff 90 0f 0b e8 d5 6a 89 ff 90 0f 0b e8 cd 6a 89 ff 90 <0f> 0b f3 0f 1e fa 4c 89 f6 48 81 e6 ff 0f 00 00 31 ff e8 95 6f 89
RSP: 0018:ffffc900046bf6d8 EFLAGS: 00010293
RAX: ffffffff820b7fa3 RBX: dffffc0000000000 RCX: ffff88802fc13c00
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff88801e97380c
RBP: ffff88801e97380c R08: ffff88801e97380f R09: 1ffff11003d2e701
R10: dffffc0000000000 R11: ffffed1003d2e702 R12: ffff88801e9737c0
R13: 1ffffffff34887b4 R14: 0000000000000002 R15: 0000000000000000
FS: 0000555570714380(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f69e1b92385 CR3: 0000000073ae6000 CR4: 0000000000350ef0
Call Trace:
<TASK>
page_table_check_free include/linux/page_table_check.h:41 [inline]
free_pages_prepare mm/page_alloc.c:1109 [inline]
free_unref_page+0xd0f/0xf20 mm/page_alloc.c:2638
dec_usb_memory_use_count+0x259/0x350 drivers/usb/core/devio.c:198
mmap_region+0x2180/0x2a30 mm/mmap.c:1574
do_mmap+0x8f0/0x1000 mm/mmap.c:496
vm_mmap_pgoff+0x1dd/0x3d0 mm/util.c:588
ksys_mmap_pgoff+0x4eb/0x720 mm/mmap.c:542
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f69e1b3c569
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 a1 1a 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:00007ffede422258 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007ffede422280 RCX: 00007f69e1b3c569
RDX: 0000000002000005 RSI: 0000000000003000 RDI: 000000002001a000
RBP: 0000000000000001 R08: 0000000000000003 R09: 0000000080000000
R10: 0000000000011012 R11: 0000000000000246 R12: 00007ffede42227c
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__page_table_check_zero+0x274/0x350 mm/page_table_check.c:157
Code: c1 0f 8c 39 fe ff ff 48 89 df e8 87 28 f3 ff e9 2c fe ff ff e8 dd 6a 89 ff 90 0f 0b e8 d5 6a 89 ff 90 0f 0b e8 cd 6a 89 ff 90 <0f> 0b f3 0f 1e fa 4c 89 f6 48 81 e6 ff 0f 00 00 31 ff e8 95 6f 89
RSP: 0018:ffffc900046bf6d8 EFLAGS: 00010293
RAX: ffffffff820b7fa3 RBX: dffffc0000000000 RCX: ffff88802fc13c00
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff88801e97380c
RBP: ffff88801e97380c R08: ffff88801e97380f R09: 1ffff11003d2e701
R10: dffffc0000000000 R11: ffffed1003d2e702 R12: ffff88801e9737c0
R13: 1ffffffff34887b4 R14: 0000000000000002 R15: 0000000000000000
FS: 0000555570714380(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f69e1b92385 CR3: 0000000073ae6000 CR4: 0000000000350ef0
----------------
Code disassembly (best guess):
0: 28 00 sub %al,(%rax)
2: 00 00 add %al,(%rax)
4: 75 05 jne 0xb
6: 48 83 c4 28 add $0x28,%rsp
a: c3 ret
b: e8 a1 1a 00 00 call 0x1ab1
10: 90 nop
11: 48 89 f8 mov %rdi,%rax
14: 48 89 f7 mov %rsi,%rdi
17: 48 89 d6 mov %rdx,%rsi
1a: 48 89 ca mov %rcx,%rdx
1d: 4d 89 c2 mov %r8,%r10
20: 4d 89 c8 mov %r9,%r8
23: 4c 8b 4c 24 08 mov 0x8(%rsp),%r9
28: 0f 05 syscall
* 2a: 48 3d 01 f0 ff ff cmp $0xfffffffffffff001,%rax <-- trapping instruction
30: 73 01 jae 0x33
32: c3 ret
33: 48 c7 c1 b8 ff ff ff mov $0xffffffffffffffb8,%rcx
3a: f7 d8 neg %eax
3c: 64 89 01 mov %eax,%fs:(%rcx)
3f: 48 rex.W


---
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If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

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#syz undup

[Hillf Danton]

On Wed, 30 Oct 2024 21:54:22 -0700

> syzbot found the following issue on:
>
> HEAD commit: 850925a8133c Merge tag '9p-for-6.12-rc5' of https://github..
> git tree: upstream

> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=158ab65f980000

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/ mm-hotfixes-unstable

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+ccc0e1...@syzkaller.appspotmail.com
Tested-by: syzbot+ccc0e1...@syzkaller.appspotmail.com

Tested on:

commit: cffcc47b mm/mlock: set the correct prev on failure
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/ mm-hotfixes-unstable
console output: https://syzkaller.appspot.com/x/log.txt?x=1548a630580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4aec7739e14231a7

dashboard link: https://syzkaller.appspot.com/bug?extid=ccc0e1cfdb72b664f0d8
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.

[Andrew Morton]

On Wed, 30 Oct 2024 21:54:22 -0700 syzbot <syzbot+ccc0e1...@syzkaller.appspotmail.com> wrote:

> Hello,
>
> syzbot found the following issue on:

Thanks. I'm suspecting some USB issue - fault injection was used to
trigger a memory allocation failure and dec_usb_memory_use_count() ended
up freeing an in-use page. Could USB folks please have a look?

[Alan Stern]

On Mon, Nov 04, 2024 at 08:00:07PM -0800, Andrew Morton wrote:
> On Wed, 30 Oct 2024 21:54:22 -0700 syzbot <syzbot+ccc0e1...@syzkaller.appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following issue on:
>
> Thanks. I'm suspecting some USB issue - fault injection was used to
> trigger a memory allocation failure and dec_usb_memory_use_count() ended
> up freeing an in-use page. Could USB folks please have a look?

Andrew, I'm not sure what to look for. Can you read through
usbdev_mmap() in drivers/usb/core/devio.c, along with the four short
routines preceding it, and let us know if anything seems obviously
wrong?

Alan Stern

[Andrew Morton]

On Tue, 5 Nov 2024 11:39:59 -0500 Alan Stern <st...@rowland.harvard.edu> wrote:

> On Mon, Nov 04, 2024 at 08:00:07PM -0800, Andrew Morton wrote:
> > On Wed, 30 Oct 2024 21:54:22 -0700 syzbot <syzbot+ccc0e1...@syzkaller.appspotmail.com> wrote:
> >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> >
> > Thanks. I'm suspecting some USB issue - fault injection was used to
> > trigger a memory allocation failure and dec_usb_memory_use_count() ended
> > up freeing an in-use page. Could USB folks please have a look?
>
> Andrew, I'm not sure what to look for.

Thanks for looking.

> Can you read through
> usbdev_mmap() in drivers/usb/core/devio.c, along with the four short
> routines preceding it, and let us know if anything seems obviously
> wrong?

All I see is lots of USB code which I don't understand ;) It seems odd
that usbdev_mmap() calls dec_usb_memory_use_count() on some error
paths, but goes direct to usbfs_decrease_memory_usage() on others.

Did you try running the "C reproducer"?

[Alan Stern]

On Tue, Nov 05, 2024 at 11:02:36AM -0800, Andrew Morton wrote:
> On Tue, 5 Nov 2024 11:39:59 -0500 Alan Stern <st...@rowland.harvard.edu> wrote:
>
> > On Mon, Nov 04, 2024 at 08:00:07PM -0800, Andrew Morton wrote:
> > > On Wed, 30 Oct 2024 21:54:22 -0700 syzbot <syzbot+ccc0e1...@syzkaller.appspotmail.com> wrote:
> > >
> > > > Hello,
> > > >
> > > > syzbot found the following issue on:
> > >
> > > Thanks. I'm suspecting some USB issue - fault injection was used to
> > > trigger a memory allocation failure and dec_usb_memory_use_count() ended
> > > up freeing an in-use page. Could USB folks please have a look?
> >
> > Andrew, I'm not sure what to look for.
>
> Thanks for looking.
>
> > Can you read through
> > usbdev_mmap() in drivers/usb/core/devio.c, along with the four short
> > routines preceding it, and let us know if anything seems obviously
> > wrong?
>
> All I see is lots of USB code which I don't understand ;) It seems odd

Well, I wouldn't expect you to understand the USB-specific stuff. I was
really asking about the memory-management calls and error handling.

> that usbdev_mmap() calls dec_usb_memory_use_count() on some error
> paths, but goes direct to usbfs_decrease_memory_usage() on others.

The paths that call dec_usb_memory_use_count() are those on which a
memory buffer has been allocated and needs to be deallocated. That
routine then calls usbfs_decrease_memory_usage() as needed.

> Did you try running the "C reproducer"?

No, I haven't. I haven't had much time to work on this. In fact, I
couldn't even tell exactly which call in dec_usb_memory_use_count()
caused the fault; the line number listed in the bug report didn't match
up with any obvious suspects in my copy of the kernel source. Was it
the kfree(usbm) call?

Alan Stern

[Andrew Morton]

Check out the sysbot commit first: 850925a8133c. Line 198 is the
hcd_buffer_free_pages() call.

hcd_buffer_free_pages() doesn't appear in the backtrace - a bunch of
things I'd expect to be present aren't there.

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 5de195060b2e251a835f622759550e6202167641
Author: Lorenzo Stoakes <lorenzo...@oracle.com>
Date: Tue Oct 29 18:11:48 2024 +0000

mm: resolve faulty mmap_region() error path behaviour

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1507b8f8580000
start commit: 850925a8133c Merge tag '9p-for-6.12-rc5' of https://github..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=309bb816d40abc28
dashboard link: https://syzkaller.appspot.com/bug?extid=ccc0e1cfdb72b664f0d8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=158ab65f980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=120e6a87980000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: mm: resolve faulty mmap_region() error path behaviour

For information about bisection process see: https://goo.gl/tpsmEJ#bisection