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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-499b90e3170sm36283225e9.5.2026.08.21.08.13.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Aug 2026 08:13:12 -0700 (PDT) Date: Fri, 21 Aug 2026 16:13:10 +0100 From: David Laight To: "Zi Yan" Cc: "Andrew Morton" , "syzbot" , , , , , , , , , , , , "Greg Kroah-Hartman" , Subject: Re: [syzbot] [mm?] WARNING in ep_write_iter Message-ID: <20260821161310.28255793@pumpkin> In-Reply-To: References: <6a820ebc.9ebadd4d.20b15e.001b.GAE@google.com> <20260816135201.98590b17b526dda8c4ec9105@linux-foundation.org> <20260821093039.04538795@pumpkin> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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... 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. David > > > > > Although the errno for 'len too big' should probably be EINVAL > > not ENOMEM. > > > > David > > > >> > >> > >> > Modules linked in: > >> > CPU: 0 UID: 0 PID: 5319 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) > >> > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 > >> > RIP: 0010:__alloc_frozen_pages_noprof+0x2ce/0x380 mm/page_alloc.c:5280 > >> > Code: 74 10 4c 89 e7 89 54 24 0c e8 0e 2c 0e 00 8b 54 24 0c 49 83 3c 24 00 0f 85 ab fe ff ff e9 ac fe ff ff c6 05 95 d2 18 0e 01 90 <0f> 0b 90 e9 17 ff ff ff a9 00 00 08 00 48 8b 4c 24 10 4c 8d 44 24 > >> > RSP: 0018:ffffc9000e13fa20 EFLAGS: 00010246 > >> > RAX: ffffc9000e13fa00 RBX: 0000000000000013 RCX: 0000000000000000 > >> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffc9000e13fa88 > >> > RBP: ffffc9000e13fb08 R08: ffffc9000e13fa87 R09: 0000000000000000 > >> > R10: ffffc9000e13fa60 R11: fffff52001c27f51 R12: 0000000000000000 > >> > R13: 1ffff92001c27f48 R14: 0000000000040cc0 R15: dffffc0000000000 > >> > FS: 00007f6f4a58c6c0(0000) GS:ffff88808c549000(0000) knlGS:0000000000000000 > >> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > >> > CR2: 00002000000010a0 CR3: 000000004323d000 CR4: 0000000000352ef0 > >> > Call Trace: > >> > > >> > alloc_pages_mpol+0x212/0x380 mm/mempolicy.c:2490 > >> > ___kmalloc_large_node+0x4c/0x120 mm/slub.c:5274 > >> > __kmalloc_large_node_noprof+0x18/0x90 mm/slub.c:5305 > >> > __do_kmalloc_node mm/slub.c:5322 [inline] > >> > __kmalloc_noprof+0x405/0x720 mm/slub.c:5359 > >> > _kmalloc_noprof include/linux/slab.h:992 [inline] > >> > ep_write_iter+0x1bc/0x500 drivers/usb/gadget/legacy/inode.c:669 > >> > new_sync_write fs/read_write.c:595 [inline] > >> > vfs_write+0x612/0xba0 fs/read_write.c:687 > >> > ksys_write+0x150/0x270 fs/read_write.c:739 > >> > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > >> > do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 > >> > entry_SYSCALL_64_after_hwframe+0x77/0x7f > >> > RIP: 0033:0x7f6f4979e0d9 > >> > Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48 > >> > RSP: 002b:00007f6f4a58bfe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 > >> > RAX: ffffffffffffffda RBX: 00007f6f49a25fa0 RCX: 00007f6f4979e0d9 > >> > RDX: 00000000ffffffb9 RSI: 0000000000000000 RDI: 0000000000000004 > >> > RBP: 00007f6f49835024 R08: 0000000000000000 R09: 0000000000000000 > >> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > >> > R13: 00007f6f49a26038 R14: 00007f6f49a25fa0 R15: 00007ffc6cf49328 > >> > > >> > > >> > >> > > > >