Message-ID: <hmzw6ng2gv6ctvgjhpttxuodpxriz63kpcnu7keywc2aioiw3v@x5xcenq5whr7>
Date: Sat, 25 Oct 2025 21:22:12 +0530
From: Gopi Krishna Menon <krishnagopi487@...il.com>
To: syzbot <syzbot+d8fd35fa6177afa8c92b@...kaller.appspotmail.com>
Cc: akpm@...ux-foundation.org, apopple@...dia.com, byungchul@...com, 
	david@...hat.com, gourry@...rry.net, joshua.hahnjy@...il.com, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, matthew.brost@...el.com, rakie.kim@...com, 
	syzkaller-bugs@...glegroups.com, ying.huang@...ux.alibaba.com, ziy@...dia.com
Subject: Re: [syzbot] [mm?] WARNING in raw_ioctl

On Fri, Oct 24, 2025 at 04:11:28PM -0700, syzbot wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    72fb0170ef1f Add linux-next specific files for 20251024
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=10fd0be2580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e812d103f45aa955
> dashboard link: https://syzkaller.appspot.com/bug?extid=d8fd35fa6177afa8c92b
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=119eae7c580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=140693e2580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/be1fa3d1f761/disk-72fb0170.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/57302bf7af40/vmlinux-72fb0170.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/91c806bb2a2b/bzImage-72fb0170.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d8fd35fa6177afa8c92b@...kaller.appspotmail.com
> 
> ------------[ cut here ]------------
> WARNING: mm/page_alloc.c:5190 at __alloc_frozen_pages_noprof+0x2c8/0x370 mm/page_alloc.c:5190, CPU#1: syz.0.17/6001
> Modules linked in:
> CPU: 1 UID: 0 PID: 6001 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
> RIP: 0010:__alloc_frozen_pages_noprof+0x2c8/0x370 mm/page_alloc.c:5190
> Code: 74 10 4c 89 e7 89 54 24 0c e8 64 b9 0d 00 8b 54 24 0c 49 83 3c 24 00 0f 85 a5 fe ff ff e9 a6 fe ff ff c6 05 b1 7d 70 0d 01 90 <0f> 0b 90 e9 18 ff ff ff a9 00 00 08 00 48 8b 4c 24 10 4c 8d 44 24
> RSP: 0018:ffffc90003017920 EFLAGS: 00010246
> RAX: ffffc90003017900 RBX: 0000000000000013 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffc90003017988
> RBP: ffffc90003017a18 R08: ffffc90003017987 R09: 0000000000000000
> R10: ffffc90003017960 R11: fffff52000602f31 R12: 0000000000000000
> R13: 1ffff92000602f28 R14: 0000000000040cc0 R15: dffffc0000000000
> FS:  000055558dedb500(0000) GS:ffff888125ddc000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007ffef4504a80 CR3: 0000000072ffa000 CR4: 00000000003526f0
> Call Trace:
>  <TASK>
>  alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2418
>  ___kmalloc_large_node+0x5f/0x1b0 mm/slub.c:5583
>  __kmalloc_large_node_noprof+0x18/0x90 mm/slub.c:5614
>  __do_kmalloc_node mm/slub.c:5630 [inline]
>  __kmalloc_noprof+0x4c9/0x800 mm/slub.c:5654
>  kmalloc_noprof include/linux/slab.h:961 [inline]
>  raw_alloc_io_data drivers/usb/gadget/legacy/raw_gadget.c:673 [inline]
>  raw_ioctl_ep_read drivers/usb/gadget/legacy/raw_gadget.c:1162 [inline]
>  raw_ioctl+0x18fb/0x3be0 drivers/usb/gadget/legacy/raw_gadget.c:1325
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:597 [inline]
>  __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fccefd8efc9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffef4505ad8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007fcceffe5fa0 RCX: 00007fccefd8efc9
> RDX: 00002000000000c0 RSI: 00000000c0085508 RDI: 0000000000000004
> RBP: 00007fccefe11f91 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fcceffe5fa0 R14: 00007fcceffe5fa0 R15: 0000000000000003
>  </TASK>
> 
> 
> ---
> 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@...glegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
> 
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup

I misunderstood what io->data is and thought of it as a buffer for
storing one packet which dosent make any sense. Since io->data is the
raw data for the transfer itself in memory, it is possible that the
transfer length is several kilo bytes in size. This is also
documented by Andrey Konovalov in his patch [1], which dropped the
transfer length checks because there can be problems with USB devices
whose configuration descriptor exceeds PAGE_SIZE in length.

But since this value comes from userspace, it is possible that the user
passes a very large value (as in syzbot's case) which would be invalid
and raise warnings in the allocator. Therefore I think we should
validate the length in raw_alloc_io_data and prevent invalid values
(values which is greater than KMALLOC_MAX_SIZE) to prevent warnings from
the allocator. 

[1] : https://lore.kernel.org/all/a6024e8eab679043e9b8a5defdb41c4bda62f02b.1761085528.git.andreyknvl@gmail.com/

#syz test


View attachment "0001-usb-raw_gadget-validate-io-length-in-raw_alloc_io_da.patch" of type "text/x-diff" (1200 bytes)

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