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gPa5GeAUVrl/52Ge5zjWwcRcIongvc7e6TfHrb2Im6j5WzoEZxr5MX1mT11eDuZALZEs4Tc2wPWaCz7DYlT/BNKIAJKxD+wLg4ys2vihMLSP0th/o+KHIwEkppD/hG9D5XoynZSsV3g61iBiRjaYAjEEzADe9+hvwRJtPZAvvi1dU57fMX7M5g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun Aug 16, 2026 at 7:32 PM EDT, Alan Stern wrote: > On Sun, Aug 16, 2026 at 05:47:34PM -0400, Zi Yan wrote: >> On Sun Aug 16, 2026 at 4:52 PM EDT, Andrew Morton wrote: >> > On Sun, 16 Aug 2026 12:25:48 -0700 syzbot wrote: >> > >> >> Hello, >> >>=20 >> >> syzbot found the following issue on: >> >>=20 >> >> HEAD commit: 3d6d817622b0 Merge tag 'scsi-fixes' of git://git.kern= el.or.. >> >> git tree: upstream >> >> console output: https://syzkaller.appspot.com/x/log.txt?x=3D159274795= 80000 >> >> kernel config: https://syzkaller.appspot.com/x/.config?x=3Da59830cba= 91a1981 >> >> dashboard link: https://syzkaller.appspot.com/bug?extid=3D805630f1453= e490427fa >> >> compiler: Debian clang version 22.1.8 (++20260613092233+e80beda= 6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 >> >>=20 >> >> Unfortunately, I don't have any reproducer for this issue yet. >> >>=20 >> >> Downloadable assets: >> >> disk image (non-bootable): https://storage.googleapis.com/syzbot-asse= ts/d900f083ada3/non_bootable_disk-3d6d8176.raw.xz >> >> vmlinux: https://storage.googleapis.com/syzbot-assets/d19e0514c02a/vm= linux-3d6d8176.xz >> >> kernel image: https://storage.googleapis.com/syzbot-assets/f6da706811= f4/bzImage-3d6d8176.xz >> >>=20 >> >> IMPORTANT: if you fix the issue, please add the following tag to the = commit: >> >> Reported-by: syzbot+805630f1453e490427fa@syzkaller.appspotmail.com >> >>=20 >> >> gadgetfs: bound to dummy_udc driver >> >> ------------[ cut here ]------------ >> >> 1 >> >> WARNING: mm/page_alloc.c:5280 at __alloc_frozen_pages_noprof+0x2ce/0x= 380 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 t= o >> > memory allocation". https://share.gemini.google/5NzjyttO0ULc >> > >> > I expect an easy fix would be >>=20 >> Maybe it is better to stop asking kmalloc for unreasonable len: >>=20 >>=20 >> diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/lega= cy/inode.c >> index d87a8ab515107..20905f254968f 100644 >> --- a/drivers/usb/gadget/legacy/inode.c >> +++ b/drivers/usb/gadget/legacy/inode.c >> @@ -645,6 +645,9 @@ ep_write_iter(struct kiocb *iocb, struct iov_iter *f= rom) >> ssize_t value; >> char *buf; >> =20 >> + if (len > KMALLOC_MAX_SIZE) >> + return -EINVAL; > > Is there any reason to think that KMALLOC_MAX_SIZE is a good limit? The= =20 > allocation could still fail, and you'd still get a WARNing. KMALLOC_MAX_SIZE uses MAX_PAGE_ORDER, anything bigger than that will be rejected by page allocator. This warning comes out because of it. This if solves the exact issue here. > > I prefer Andrew's first suggestion. If the user asks the kernel to copy= =20 > too much data, just fail -- with no warning. __GFP_WARN gets rid of all other warnings, even if user asks for a reasonable size. Why use such a big hammer? --=20 Best Regards, Yan, Zi