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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-499b90d67bfsm19315855e9.3.2026.08.21.01.30.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Aug 2026 01:30:44 -0700 (PDT) Date: Fri, 21 Aug 2026 09:30:39 +0100 From: David Laight To: Andrew Morton Cc: 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, ziy@nvidia.com, Greg Kroah-Hartman , linux-usb@vger.kernel.org Subject: Re: [syzbot] [mm?] WARNING in ep_write_iter Message-ID: <20260821093039.04538795@pumpkin> In-Reply-To: <20260816135201.98590b17b526dda8c4ec9105@linux-foundation.org> References: <6a820ebc.9ebadd4d.20b15e.001b.GAE@google.com> <20260816135201.98590b17b526dda8c4ec9105@linux-foundation.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; 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"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' ? 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 > > > > > >