CVE-2022-50704 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
USB: gadget: Fix use-after-free during usb config switch
In the process of switching USB config from rndis to other config, if the hardware does not support the ->pullup callback, or the hardware encounters a low probability fault, both of them may cause the ->pullup callback to fail, which will then cause a system panic (use after free).
The gadget drivers sometimes need to be unloaded regardless of the hardware's behavior.
Analysis as follows: ======================================================================= (1) write /config/usb_gadget/g1/UDC "none"
gether_disconnect+0x2c/0x1f8 rndis_disable+0x4c/0x74 composite_disconnect+0x74/0xb0 configfs_composite_disconnect+0x60/0x7c usb_gadget_disconnect+0x70/0x124 usb_gadget_unregister_driver+0xc8/0x1d8 gadget_dev_desc_UDC_store+0xec/0x1e4
(2) rm /config/usb_gadget/g1/configs/b.1/f1
rndis_deregister+0x28/0x54 rndis_free+0x44/0x7c usb_put_function+0x14/0x1c config_usb_cfg_unlink+0xc4/0xe0 configfs_unlink+0x124/0x1c8 vfs_unlink+0x114/0x1dc
(3) rmdir /config/usb_gadget/g1/functions/rndis.gs4
panic+0x1fc/0x3d0 do_page_fault+0xa8/0x46c do_mem_abort+0x3c/0xac el1_sync_handler+0x40/0x78 0xffffff801138f880 rndis_close+0x28/0x34 eth_stop+0x74/0x110 dev_close_many+0x48/0x194 rollback_registered_many+0x118/0x814 unregister_netdev+0x20/0x30 gether_cleanup+0x1c/0x38 rndis_attr_release+0xc/0x14 kref_put+0x74/0xb8 configfs_rmdir+0x314/0x374
If gadget->ops->pullup() return an error, function rndis_close() will be called, then it will causes a use-after-free problem. =======================================================================
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Analysis
by VulDB Data Team • 02/24/2026
The vulnerability described in CVE-2022-50704 represents a critical use-after-free condition within the Linux kernel's USB gadget subsystem that can lead to system panics and potential denial of service scenarios. This flaw specifically manifests during USB configuration switching operations when transitioning from RNDIS (Remote Network Driver Interface Specification) configurations to other USB configurations. The issue stems from improper handling of hardware callback failures, particularly when the USB gadget controller does not support the ->pullup callback mechanism or encounters rare hardware faults that cause this callback to fail. According to CWE-416, this vulnerability directly maps to a use-after-free condition where memory is accessed after it has been freed, creating a dangerous state that can be exploited to cause system instability or potentially enable privilege escalation attacks. The vulnerability operates through the USB gadget framework's configuration management system where the kernel attempts to clean up RNDIS function resources during configuration switches, but fails to properly validate the state of hardware callbacks before proceeding with memory deallocation.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise the entire USB gadget infrastructure within embedded systems and devices that rely on Linux kernel USB functionality. When the ->pullup callback returns an error, the system flow triggers rndis_close() which subsequently calls eth_stop() and dev_close_many() functions that attempt to unregister network devices. This sequence leads to a cascade of cleanup operations where memory allocated to RNDIS function structures becomes freed but then accessed later during the configuration removal process. The ATT&CK framework categorizes this as a system service interruption technique under T1490, as the vulnerability can be leveraged to cause persistent system instability. The specific call chain demonstrates how the vulnerability propagates through the kernel's USB gadget subsystem where the gadget driver's disconnect mechanism fails to properly handle error conditions from hardware callbacks, leading to memory corruption. The panic occurs at the page fault handler level when the system attempts to access memory that has already been deallocated, as evidenced by the do_page_fault and do_mem_abort function calls in the stack trace.
Mitigation strategies for CVE-2022-50704 must address both immediate kernel-level protections and broader system hardening measures to prevent exploitation of the use-after-free condition. The primary fix involves implementing proper error handling within the USB gadget subsystem to ensure that when ->pullup callbacks fail, the system does not proceed with memory deallocation operations that could lead to use-after-free scenarios. This requires modifications to the gadget driver's disconnect logic to validate callback results before initiating cleanup sequences and to maintain proper reference counting mechanisms throughout the configuration switching process. Organizations should prioritize applying the kernel patches that address this specific vulnerability, particularly in embedded systems, IoT devices, and any hardware platforms that utilize USB gadget functionality for network connectivity. The fix should include enhanced error recovery mechanisms that prevent the system from entering an inconsistent state when hardware callbacks fail, ensuring that cleanup operations only proceed when all prerequisites are satisfied. Additionally, system administrators should implement monitoring solutions that can detect unusual USB gadget behavior patterns, as the vulnerability may be exploitable in scenarios where attackers can force configuration switches to trigger the problematic code path. The vulnerability's presence in the Linux kernel's USB gadget framework makes it particularly dangerous for network appliances, industrial control systems, and embedded devices that rely on USB gadget functionality for remote management or data transfer operations.