CVE-2025-71274

In the Linux kernel, the following vulnerability has been resolved:

rpmsg: core: fix race in driver_override_show() and use core helper

The driver_override_show function reads the driver_override string without holding the device_lock. However, the store function modifies and frees the string while holding the device_lock. This creates a race condition where the string can be freed by the store function while being read by the show function, leading to a use-after-free.

To fix this, replace the rpmsg_string_attr macro with explicit show and store functions. The new driver_override_store uses the standard driver_set_override helper. Since the introduction of driver_set_override, the comments in include/linux/rpmsg.h have stated that this helper must be used to set or clear driver_override, but the implementation was not updated until now.

Because driver_set_override modifies and frees the string while holding the device_lock, the new driver_override_show now correctly holds the device_lock during the read operation to prevent the race.

Additionally, since rpmsg_string_attr has only ever been used for driver_override, removing the macro simplifies the code.

Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://git.kernel.org/stable/c/2e4a70f3c30910427e5ea848b799066d67b963d5
• https://git.kernel.org/stable/c/392c6b68334aa0e0ae9aba95c0a366bcb0d92f5d
• https://git.kernel.org/stable/c/42023d4b6d2661a40ee2dcf7e1a3528a35c638ca
• https://git.kernel.org/stable/c/47615557447185917afa432b7958f87583c417cb
• https://git.kernel.org/stable/c/7654e6e3cd6bdee9602f6063b3c670bd556d7e61
• https://git.kernel.org/stable/c/90c8353f471821d7ccd4fe573a2402e056192494
• https://git.kernel.org/stable/c/954557957177c3c13d7c655976665b1170da5e50
• https://git.kernel.org/stable/c/d66b8074c555e8abb0ae19eea1c9f3635498bdde