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Tue, 11 Aug 2026 09:06:10 -0700 (PDT) From: Jeffin Philip To: valentina.manea.m@gmail.com, shuah@kernel.org, gregkh@linuxfoundation.org Cc: i@zenithal.me, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, syzbot+af76b01c9a0f0ab60fb0@syzkaller.appspotmail.com, Jeffin Philip Subject: [PATCH v3 1/2] usbip: usbip_host: fix null pointer dereference in rebind_store Date: Tue, 11 Aug 2026 21:35:40 +0530 Message-ID: <20260811160541.29461-2-jeffinphilip14@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260811160541.29461-1-jeffinphilip14@gmail.com> References: <20260811160541.29461-1-jeffinphilip14@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" rebind_store drops locks to execute do_rebind which sleeps during which time udev may become NULL due to physical disconnect. Since this cannot be prevented and spinlocks cannot be obtained in do_rebind, we turn towards the function that performs the same action, drivers_probe, safely. Remove rebind_store and print a warning to the user to use drivers_probe instead as a safer alternative. Reported-by: syzbot+af76b01c9a0f0ab60fb0@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Daf76b01c9a0f0ab60fb0 Fixes: 4bfb141bc013 ("usbip: usbip_host: fix to hold parent lock for device= _attach() calls") Cc: stable@vger.kernel.org Signed-off-by: Jeffin Philip --- Changes in v3: - Addressed the race condition proposed by Greg KH in v2 discussion. Changes in v2: - Addressed concerns raised by the Greg KH in v1 discussion - Added usb_get_dev() to get a reference to udev preventing it from becoming null after the null check. Drop the reference after using it in do_rebind() v1: - Initial patch with a udev null check that returns -ENODEV if udev is null. --- drivers/usb/usbip/stub_main.c | 27 +-------------------------- 1 file changed, 1 insertion(+), 26 deletions(-) diff --git a/drivers/usb/usbip/stub_main.c b/drivers/usb/usbip/stub_main.c index 79110a69d697..013f1563b1e9 100644 --- a/drivers/usb/usbip/stub_main.c +++ b/drivers/usb/usbip/stub_main.c @@ -242,32 +242,7 @@ static void stub_device_rebind(void) static ssize_t rebind_store(struct device_driver *dev, const char *buf, size_t count) { - int ret; - int len; - struct bus_id_priv *bid; - - /* buf length should be less that BUSID_SIZE */ - len =3D strnlen(buf, BUSID_SIZE); - - if (!(len < BUSID_SIZE)) - return -EINVAL; - - bid =3D get_busid_priv(buf); - if (!bid) - return -ENODEV; - - /* mark the device for deletion so probe ignores it during rescan */ - bid->status =3D STUB_BUSID_OTHER; - /* release the busid lock */ - put_busid_priv(bid); - - ret =3D do_rebind((char *) buf, bid); - if (ret < 0) - return ret; - - /* delete device from busid_table */ - del_match_busid((char *) buf); - + pr_warn("rebind node is deprecated, consider using drivers_probe instead\= n"); return count; } -- 2.55.0 From nobody Tue Sep 29 06:49:52 2026 Received: from mail-pg1-f173.google.com (mail-pg1-f173.google.com [209.85.215.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B7F523CC7DC for ; Tue, 11 Aug 2026 16:06:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786464385; cv=none; b=TNkvIdhz9iulBEicuaLHEl/5v8U7zgxJHAZtFEMAyeOCDLmcJ2Wq14IIJ1UxSAkVRCIt+OTDLlTGW5TTfvmodUj9auUeFX9SM/DlzjXxHzhZtnhV+EFGqg9HnvdL1SYsE0Tt65xws00w5H1/1/ZxCk8gkvxDdVNU7shUn92qe/s= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786464385; c=relaxed/simple; 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Tue, 11 Aug 2026 09:06:22 -0700 (PDT) Received: from Default ([2409:40f4:1011:30f7:310c:32cf:5ea7:7043]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-31cf3624c08sm916149eec.5.2026.08.11.09.06.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Aug 2026 09:06:21 -0700 (PDT) From: Jeffin Philip To: valentina.manea.m@gmail.com, shuah@kernel.org, gregkh@linuxfoundation.org Cc: i@zenithal.me, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, syzbot+af76b01c9a0f0ab60fb0@syzkaller.appspotmail.com, Jeffin Philip Subject: [PATCH v3 2/2] usbip: tools: replace faulty rebind_store with drivers_probe Date: Tue, 11 Aug 2026 21:35:41 +0530 Message-ID: <20260811160541.29461-3-jeffinphilip14@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260811160541.29461-1-jeffinphilip14@gmail.com> References: <20260811160541.29461-1-jeffinphilip14@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" unbind_device() currently unbinds and then uses rebind_store to rebind the device back to the usb driver. This is already possible with the safer drivers_probe rather than the faulty rebind_store. Fix this by referencing drivers_probe rather than rebind_store. Fixes: a46034ca57ed ("staging: usbip: trigger driver probing after unbindin= g from usbip-host") Signed-off-by: Jeffin Philip --- tools/usb/usbip/src/usbip_unbind.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/tools/usb/usbip/src/usbip_unbind.c b/tools/usb/usbip/src/usbip= _unbind.c index 66a44d4a0d56..242280cec452 100644 --- a/tools/usb/usbip/src/usbip_unbind.c +++ b/tools/usb/usbip/src/usbip_unbind.c @@ -34,7 +34,7 @@ static int unbind_device(char *busid) =20 char unbind_attr_name[] =3D "unbind"; char unbind_attr_path[SYSFS_PATH_MAX]; - char rebind_attr_name[] =3D "rebind"; + char rebind_attr_name[] =3D "drivers_probe"; char rebind_attr_path[SYSFS_PATH_MAX]; =20 struct udev *udev; @@ -77,9 +77,8 @@ static int unbind_device(char *busid) } =20 /* Trigger new probing. */ - snprintf(rebind_attr_path, sizeof(unbind_attr_path), "%s/%s/%s/%s/%s/%s", - SYSFS_MNT_PATH, SYSFS_BUS_NAME, bus_type, SYSFS_DRIVERS_NAME, - USBIP_HOST_DRV_NAME, rebind_attr_name); + snprintf(rebind_attr_path, sizeof(rebind_attr_path), "%s/%s/%s/%s", + SYSFS_MNT_PATH, SYSFS_BUS_NAME, bus_type, rebind_attr_name); =20 rc =3D write_sysfs_attribute(rebind_attr_path, busid, strlen(busid)); if (rc < 0) { -- 2.55.0