CVE-2025-21739

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_hbas 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 theyve 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
  its not needed anymore
* no future drivers using ufshcd_alloc_host() could ever forget
  adding the cleanup

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/0c77c0d754fe83cb154715fcfec6c3faef94f207
• https://git.kernel.org/stable/c/9c185beae09a3eb85f54777edafa227f7e03075d
• https://git.kernel.org/stable/c/f8fb2403ddebb5eea0033d90d9daae4c88749ada