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b=fAiGVgVECPqcAhs97DVvyJ6sVWl94Hg/LZgwPbnkAVbHokg/SnVXt3owQSgxwXwLH JcEfrZXMoajK4lt9Gegen1S2L7SlgdF/nSWtUjh6qJ6I8QovCGuCkOlR2310ni2F2g Gs6RSMoetM94NEfuREDb03iyJPMscvUm84mvA7A4qC4XgNC2ConhRJ41hGGPO7dch1 M5QaOfuV9SW20ds31Hr8B82LfMwC1BeY2S1blewCN5FrjOgA89gmqTgKmtvoENONqI QLnD7hrK2N9T5KOc8wH9cUUoX8eIe9gINNYo1qRCHG3HLv/uIqVFRKqbUQkLvnFEtN gCyJZDnOoZ+8w== Message-ID: <733d4be4-2983-4591-9769-e2ccd64191d6@kernel.org> Date: Wed, 26 Aug 2026 12:26:10 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [mm?] WARNING in ep_write_iter Content-Language: en-US To: Zi Yan , David Laight , Harry Yoo Cc: Andrew Morton , syzbot , apopple@nvidia.com, byungchul@sk.com, david@kernel.org, gourry@gourry.net, joshua.hahnjy@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, matthew.brost@intel.com, rakie.kim@sk.com, syzkaller-bugs@googlegroups.com, ying.huang@linux.alibaba.com, Greg Kroah-Hartman , linux-usb@vger.kernel.org References: <6a820ebc.9ebadd4d.20b15e.001b.GAE@google.com> <20260816135201.98590b17b526dda8c4ec9105@linux-foundation.org> <20260821093039.04538795@pumpkin> <20260821161310.28255793@pumpkin> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 5FF6540003 X-Stat-Signature: gm815oofy8costqnnkuwnfskmofm3d85 X-Rspam-User: X-HE-Tag: 1787739976-544675 X-HE-Meta: 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 /0jwyUL7 PI22U3OcUEl7+MNii1RJClJ4aIOKW+yeLm+tm4tJdSb5HJSsmXE8RYEXBsMIXWvi5HT1fdsdfSzia3uoPD695pvjGHadRHBZx7xBEb18YCKJYRPJp3t8A5Yifw8EAIf5KGpVlIWojJ7Cs7GaWqsfZ3zTo38gRDuWai+ziq/g/VsK4Be98KUIkMusXxO/C3Tmlopl8FRwgvI9LoFE1P8R2irokfjuea9Z2UsjYR4gRF7GpDw9kZKFLODm9u6KtsTMzVIkepU5DhqqEmmDz2l/c4CvOziXlCzK3C92yEJxzC1Z52VxrYNOv7mkOOaud1xEY8A7acyn9bTgI8nnp58wzI2hcT1tCHdgAxf0urY3fi3eLojgj2ztHlGYJr1A05CqQZLtB7jLqEblePjlbEfGRY7WnUrjTWaau5aZegvNTzQJ9Q0vzh7IYB99ZbX6CKe6UWeG64nT8NbEoEJaNTZV77b2pUGGrU2HoA5mvMIJUCk7TZIVNPSWV44/sDCqs0vnD3I/qLORNYX8xYjK0ovu7i4QOAuRlxV9saR237/7os8kHm0WXSuQ6PSI/BHbAOiXIuKRpnluuZboUpGQ/WP9qo5Yb+t14hxa8BjieD4boc5KgfRBieFnNOz/cGsB7FDsArI15Ptf0KO39DMhHUD8GTkD8+fVdDxkwHqO1kT1ifrjS+RSxd3e74NU6LwyvmhDMU4Y7+Vo7hfvINkLPCmG5vhgpqIT9bJdSQh/p/eLGT+M4tZ9SoP1W6zJeBGSJl04M0k9Q5yqKxKvNHskNyGN8hKPLSb5sxJfmDKfWgRyYkCn74amdME0SK3zuzS5OiguHPoOBFw9wqkoewl7hFvi7vSHiBcCo7WSbgfw4+w7HFMQAof6xgugP3E/WgtckSQKxSoee7c8THBc47w0fKSvFBVWMdsj6TBhGw7KWkxz3gfezAb2WGVvSvxhkGnk2qdk6RMyI6kW+2F424u6BOrzUXWfNYG8k BHXVarbM w8Y3Srx2dbYBnZltZ3Nicy19GnZIPcwUFeLxtDY+aMiMRt3AHFNV/569v51bm+OAq8mHNAG8FXfOWrY6CGTk4+NOZW2FSzlBLxpLUq3SEetnWuTgZeeA2bEgPEXlX7tgSG3JIvMbCBObtcN2mndG8g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/21/26 17:31, Zi Yan wrote: > On 21 Aug 2026, at 11:13, David Laight wrote: > >> On Fri, 21 Aug 2026 10:24:36 -0400 >> "Zi Yan" wrote: >> >>> On Fri Aug 21, 2026 at 4:30 AM EDT, David Laight wrote: >>>> On Sun, 16 Aug 2026 13:52:01 -0700 >>>> Andrew Morton wrote: >>>> >>>>> On Sun, 16 Aug 2026 12:25:48 -0700 syzbot wrote: >>>>> >>>>>> Hello, >>>>>> >>>>>> syzbot found the following issue on: >>>>>> >>>>>> HEAD commit: 3d6d817622b0 Merge tag 'scsi-fixes' of git://git.kernel.or.. >>>>>> git tree: upstream >>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=15927479580000 >>>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=a59830cba91a1981 >>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=805630f1453e490427fa >>>>>> compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 >>>>>> >>>>>> Unfortunately, I don't have any reproducer for this issue yet. >>>>>> >>>>>> Downloadable assets: >>>>>> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-3d6d8176.raw.xz >>>>>> vmlinux: https://storage.googleapis.com/syzbot-assets/d19e0514c02a/vmlinux-3d6d8176.xz >>>>>> kernel image: https://storage.googleapis.com/syzbot-assets/f6da706811f4/bzImage-3d6d8176.xz >>>>>> >>>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit: >>>>>> Reported-by: syzbot+805630f1453e490427fa@syzkaller.appspotmail.com >>>>>> >>>>>> gadgetfs: bound to dummy_udc driver >>>>>> ------------[ cut here ]------------ >>>>>> 1 >>>>>> WARNING: mm/page_alloc.c:5280 at __alloc_frozen_pages_noprof+0x2ce/0x380 mm/page_alloc.c:5280, CPU#0: syz.0.0/5319 >>>>> >>>>> Thanks. drivers/usb/gadget is the offender. >>>>> >>>>> Gemini sums it up well. "ep_write_iter() needs a bounds check prior to >>>>> memory allocation". https://share.gemini.google/5NzjyttO0ULc >>>>> >>>>> I expect an easy fix would be >>>>> >>>>> --- a/drivers/usb/gadget/legacy/inode.c~a >>>>> +++ a/drivers/usb/gadget/legacy/inode.c >>>>> @@ -666,7 +666,7 @@ ep_write_iter(struct kiocb *iocb, struct >>>>> return -EBADMSG; >>>>> } >>>>> >>>>> - buf = kmalloc(len, GFP_KERNEL); >>>>> + buf = kmalloc(len, GFP_KERNEL|__GFP_NOWARN); >>>>> if (unlikely(!buf)) { >>>>> mutex_unlock(&epdata->lock); >>>>> return -ENOMEM; >>>>> >>>>> or do what Gemini said. Me, I'll add some cc's and run away. >>>> >>>> Should there be a separate flags for 'request too large' and >>>> 'no memory available' ? >>> >>> What flags? Are you suggesting kmalloc should return an ERR_PTR to >>> distinguish different error types? >> >> That would break to much... > > +Vlastimil and Harry on this. Maybe worth giving it a try. We would have to change every existing caller to check for ERR_PTR instead of just NULL check? Not worth it IMHO. >> I was thinking of a GFP_NOWARN_TOOBIG. >> >> That isn't enough to change the errno though. >> But a smaller sanity limit may make sense anyway. > > Maybe. I am not sure if we want to spend a GFP flag for that. Agreed, those are scarce and this is not worth it either. Maybe a wrapper for kmalloc() for "allocations with potentially untrusted unsanitized size" could be made (we can always increase the existing wrapper hell...). > Best Regards, > Yan, Zi