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Fri, 11 Sep 2026 02:01:44 -0700 (PDT) From: Chaithanya Lagisetty To: Greg KH Cc: Christophe JAILLET , Kees Cook , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+28cf08dec5895bd562e6@syzkaller.appspotmail.com, Chaithanya Lagisetty Subject: Re: [PATCH RESEND] usb: gadget: f_loopback: fix descriptor leak on unbind Date: Fri, 11 Sep 2026 09:01:36 +0000 Message-ID: <20260911090136.64549-1-nagachaithanya9911@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <2026091028-launder-jockstrap-be0c@gregkh> References: <20260808181504.462492-1-nagachaithanya9911@gmail.com> <20260902105153.3516793-1-nagachaithanya9911@gmail.com> <2026091028-launder-jockstrap-be0c@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Thu, Sep 10, 2026 at 06:32:50PM +0200, Greg KH wrote: > How was this tested? I don't see syzbot doing the test, did you? I ran the syzbot reproducer from the reported bug against both an unpatched and a patched kernel. Both kernels were built from the same source tree and .config, with the same compiler and QEMU environment; the patch was the only difference. On the unpatched kernel, the reproducer triggered 3 "BUG: memory leak" reports in 5 iterations. All reported allocations originated from loopback_bind() through usb_assign_descriptors() / usb_copy_descriptors(): BUG: memory leak unreferenced object 0xffff888016dad4c0 (size 64): comm "repro", pid 5597, jiffies 4294942168 backtrace (crc c8d54481): __kmalloc_noprof+0x391/0x540 usb_copy_descriptors+0x6c/0x170 usb_assign_descriptors+0x6c/0x180 loopback_bind+0xf4/0x130 usb_add_function+0xca/0x270 configfs_composite_bind+0x6dc/0xa90 gadget_bind_driver+0xf7/0x3e0 ... gadget_dev_desc_UDC_store+0x153/0x1e0 On the patched kernel, I ran 25 reproducer iterations and observed no "BUG: memory leak" reports. I also performed three explicit kmemleak scans, all of which were clean. > And did you forget an Assisted-by: tag? Yes, I did. I will add: Assisted-by: Cursor:opus-5 in the next revision. Regards, Chaithanya