[syzbot] [usb?] memory leak in hidg_bind

[syzbot] [usb?] memory leak in hidg_bind

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    9a143525f62b Merge tag 'ata-7.2-rc7' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17edefb9580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6843f8fd2336602d
dashboard link: https://syzkaller.appspot.com/bug?extid=60740c6a17a5b5eb1f5a
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1061fe49580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10c06fb9580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/689093bae5bf/disk-9a143525.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a57b87e6032d/vmlinux-9a143525.xz
kernel image: https://storage.googleapis.com/syzbot-assets/508c649c8b0f/bzImage-9a143525.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+60740c6a17a5b5eb1f5a@syzkaller.appspotmail.com

2026/08/08 09:35:22 executed programs: 5
BUG: memory leak
unreferenced object 0xffff888112450300 (size 128):
  comm "syz.0.18", pid 5923, jiffies 4294943868
  hex dump (first 32 bytes):
    00 03 45 12 81 88 ff ff 00 03 45 12 81 88 ff ff  ..E.......E.....
    30 00 b2 03 81 88 ff ff 00 00 00 00 00 00 00 00  0...............
  backtrace (crc 18381426):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4597 [inline]
    slab_alloc_node mm/slub.c:4917 [inline]
    __kmalloc_cache_noprof+0x356/0x440 mm/slub.c:5485
    _kmalloc_noprof include/linux/slab.h:988 [inline]
    _kzalloc_noprof include/linux/slab.h:1309 [inline]
    dummy_alloc_request+0x65/0xf0 drivers/usb/gadget/udc/dummy_hcd.c:693
    usb_ep_alloc_request+0x2e/0xd0 drivers/usb/gadget/udc/core.c:197
    hidg_bind+0x2b/0x490 drivers/usb/gadget/function/f_hid.c:1154
    usb_add_function+0xca/0x270 drivers/usb/gadget/composite.c:333
    configfs_composite_bind+0x667/0x9b0 drivers/usb/gadget/configfs.c:1802
    gadget_bind_driver+0xed/0x390 drivers/usb/gadget/udc/core.c:1662
    call_driver_probe drivers/base/dd.c:628 [inline]
    really_probe+0x12f/0x3a0 drivers/base/dd.c:706
    __driver_probe_device+0xe9/0x1a0 drivers/base/dd.c:868
    driver_probe_device+0x28/0xf0 drivers/base/dd.c:898
    __driver_attach drivers/base/dd.c:1292 [inline]
    __driver_attach+0x10a/0x200 drivers/base/dd.c:1232
    bus_for_each_dev+0xb8/0x120 drivers/base/bus.c:383
    bus_add_driver+0x122/0x280 drivers/base/bus.c:763
    driver_register+0xb1/0x140 drivers/base/driver.c:174
    usb_gadget_register_driver_owner+0x69/0xe0 drivers/usb/gadget/udc/core.c:1752
    gadget_dev_desc_UDC_store+0x153/0x1e0 drivers/usb/gadget/configfs.c:300

BUG: memory leak
unreferenced object 0xffff888112c7bf00 (size 128):
  comm "syz.0.20", pid 5967, jiffies 4294944502
  hex dump (first 32 bytes):
    00 bf c7 12 81 88 ff ff 00 bf c7 12 81 88 ff ff  ................
    30 00 b2 03 81 88 ff ff 00 00 00 00 00 00 00 00  0...............
  backtrace (crc cd50bb2e):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4597 [inline]
    slab_alloc_node mm/slub.c:4917 [inline]
    __kmalloc_cache_noprof+0x356/0x440 mm/slub.c:5485
    _kmalloc_noprof include/linux/slab.h:988 [inline]
    _kzalloc_noprof include/linux/slab.h:1309 [inline]
    dummy_alloc_request+0x65/0xf0 drivers/usb/gadget/udc/dummy_hcd.c:693
    usb_ep_alloc_request+0x2e/0xd0 drivers/usb/gadget/udc/core.c:197
    hidg_bind+0x2b/0x490 drivers/usb/gadget/function/f_hid.c:1154
    usb_add_function+0xca/0x270 drivers/usb/gadget/composite.c:333
    configfs_composite_bind+0x667/0x9b0 drivers/usb/gadget/configfs.c:1802
    gadget_bind_driver+0xed/0x390 drivers/usb/gadget/udc/core.c:1662
    call_driver_probe drivers/base/dd.c:628 [inline]
    really_probe+0x12f/0x3a0 drivers/base/dd.c:706
    __driver_probe_device+0xe9/0x1a0 drivers/base/dd.c:868
    driver_probe_device+0x28/0xf0 drivers/base/dd.c:898
    __driver_attach drivers/base/dd.c:1292 [inline]
    __driver_attach+0x10a/0x200 drivers/base/dd.c:1232
    bus_for_each_dev+0xb8/0x120 drivers/base/bus.c:383
    bus_add_driver+0x122/0x280 drivers/base/bus.c:763
    driver_register+0xb1/0x140 drivers/base/driver.c:174
    usb_gadget_register_driver_owner+0x69/0xe0 drivers/usb/gadget/udc/core.c:1752
    gadget_dev_desc_UDC_store+0x153/0x1e0 drivers/usb/gadget/configfs.c:300

connection error: failed to recv *flatrpc.ExecutorMessageRawT: EOF


---
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[PATCH] USB: gadget: f_hid: Release get report req upon unsetup

[Edward Adam Davis]

The GET_REPORT request instance (hidg->get_req) is freed only within
hidg_disable() after successful binding, and only if Condition [1] is met.

Since userspace does not execute the setup, get_report_workqueue_handler()
is never invoked; consequently, Condition [1] is never met, leading to the
memory leak reported in [2].

The solution is to add memory reclamation for get_req in hidg_unbind(),
using `get_req->length` to determine whether Condition [1] applies.

Additionally, a failure in usb_gstrings_attach() also triggers the issue
reported in [2], so this is fixed at the same time.

[1]
The report is not in the list or should not be sent immediately

[2]
BUG: memory leak
unreferenced object 0xffff888112450300 (size 128):
  backtrace (crc 18381426):
    usb_ep_alloc_request+0x2e/0xd0 drivers/usb/gadget/udc/core.c:197
    hidg_bind+0x2b/0x490 drivers/usb/gadget/function/f_hid.c:1154
    usb_add_function+0xca/0x270 drivers/usb/gadget/composite.c:333
    configfs_composite_bind+0x667/0x9b0 drivers/usb/gadget/configfs.c:1802
    gadget_bind_driver+0xed/0x390 drivers/usb/gadget/udc/core.c:1662


Fixes: a139c98f760e ("USB: gadget: f_hid: Add GET_REPORT via userspace IOCTL")
Reported-by: syzbot+60740c6a17a5b5eb1f5a@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=60740c6a17a5b5eb1f5a
Tested-by: syzbot+60740c6a17a5b5eb1f5a@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
 drivers/usb/gadget/function/f_hid.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
index 3c6b43d06a6d..8d739e052e68 100644
--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -1163,8 +1163,10 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
 	/* maybe allocate device-global string IDs, and patch descriptors */
 	us = usb_gstrings_attach(c->cdev, ct_func_strings,
 				 ARRAY_SIZE(ct_func_string_defs));
-	if (IS_ERR(us))
-		return PTR_ERR(us);
+	if (IS_ERR(us)) {
+		status = PTR_ERR(us);
+		goto fail;
+	}
 	hidg_interface_desc.iInterface = us[CT_FUNC_HID_IDX].id;
 
 	/* allocate instance-specific interface IDs, and patch descriptors */
@@ -1585,10 +1587,18 @@ static void hidg_free(struct usb_function *f)
 static void hidg_unbind(struct usb_configuration *c, struct usb_function *f)
 {
 	struct f_hidg *hidg = func_to_hidg(f);
+	unsigned long flags;
 
 	cdev_device_del(hidg->cdev, &hidg->dev);
 	destroy_workqueue(hidg->workqueue);
 	usb_free_all_descriptors(f);
+
+	spin_lock_irqsave(&hidg->get_report_spinlock, flags);
+	if (hidg->get_req && !hidg->get_req->length) {
+		usb_ep_free_request(f->config->cdev->gadget->ep0, hidg->get_req);
+		hidg->get_req = NULL;
+	}
+	spin_unlock_irqrestore(&hidg->get_report_spinlock, flags);
 }
 
 static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
-- 
2.43.0