CVE-2025-21739
Published: 27 February 2025
Description
In the Linux kernel, the following vulnerability has been resolved: scsi: ufs: core: Fix use-after free in init error and remove paths devm_blk_crypto_profile_init() registers a cleanup handler to run when the associated (platform-) device is being released. For UFS, the crypto private data and pointers are stored as part of the ufs_hba's data structure 'struct ufs_hba::crypto_profile'. This structure is allocated as part of the underlying ufshcd and therefore Scsi_host allocation. During driver release or during error handling in ufshcd_pltfrm_init(), this structure is released as part of ufshcd_dealloc_host() before the (platform-) device associated with the crypto call above is released. Once this device is released, the crypto cleanup code will run, using the just-released 'struct ufs_hba::crypto_profile'. This causes a use-after-free situation: Call trace: kfree+0x60/0x2d8 (P) kvfree+0x44/0x60 blk_crypto_profile_destroy_callback+0x28/0x70 devm_action_release+0x1c/0x30 release_nodes+0x6c/0x108 devres_release_all+0x98/0x100 device_unbind_cleanup+0x20/0x70 really_probe+0x218/0x2d0 In other words, the initialisation code flow is: platform-device probe ufshcd_pltfrm_init() ufshcd_alloc_host() scsi_host_alloc() allocation of struct ufs_hba creation of scsi-host devices devm_blk_crypto_profile_init() devm registration of cleanup handler using platform-device and during error handling of ufshcd_pltfrm_init() or during driver removal: ufshcd_dealloc_host() scsi_host_put() put_device(scsi-host) release of struct ufs_hba put_device(platform-device) crypto cleanup handler To fix this use-after free, change ufshcd_alloc_host() to register a devres action to automatically cleanup the underlying SCSI device on ufshcd destruction, without requiring explicit calls to ufshcd_dealloc_host(). This way: * the crypto profile and all other ufs_hba-owned resources are destroyed before SCSI (as they've been registered after) * a memleak is plugged in tc-dwc-g210-pci.c remove() as a side-effect * EXPORT_SYMBOL_GPL(ufshcd_dealloc_host) can be removed fully as it's not needed anymore * no future drivers using ufshcd_alloc_host() could ever forget adding the cleanup
Security Summary
CVE-2025-21739 is a use-after-free vulnerability in the Linux kernel's SCSI UFS core subsystem, specifically in the initialization error handling and driver removal paths. The issue arises because devm_blk_crypto_profile_init() registers a cleanup handler tied to the platform device, but the associated struct ufs_hba::crypto_profile data is freed earlier during ufshcd_dealloc_host() as part of SCSI host deallocation. This leads to the crypto cleanup code accessing the already-freed memory when the platform device is later released, as evidenced by the call trace involving kfree, kvfree, and blk_crypto_profile_destroy_callback.
A local attacker with low privileges can exploit this vulnerability due to its CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H). Exploitation requires triggering the affected initialization error paths in ufshcd_pltfrm_init() or normal driver removal, potentially allowing arbitrary code execution, data corruption, or system crashes through manipulation of the freed ufs_hba crypto profile structure.
The provided patch references from kernel.org stable repositories detail the mitigation, which modifies ufshcd_alloc_host() to register a devres action for automatic SCSI device cleanup on ufshcd destruction. This ensures the crypto profile and other ufs_hba resources are destroyed before the SCSI host, prevents the use-after-free, plugs a related memory leak in tc-dwc-g210-pci.c, eliminates the need for EXPORT_SYMBOL_GPL(ufshcd_dealloc_host), and safeguards future drivers using ufshcd_alloc_host() against similar cleanup oversights.
Details
- CWE(s)