CVE-2021-47653

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

media: davinci: vpif: fix use-after-free on driver unbind

The driver allocates and registers two platform device structures during probe, but the devices were never deregistered on driver unbind.

This results in a use-after-free on driver unbind as the device structures were allocated using devres and would be freed by driver core when remove() returns.

Fix this by adding the missing deregistration calls to the remove() callback and failing probe on registration errors.

Note that the platform device structures must be freed using a proper release callback to avoid leaking associated resources like device names.

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/43acb728bbc40169d2e2425e84a80068270974be
• https://git.kernel.org/stable/c/6512c3c39cb6b573b791ce45365818a38b76afbe
• https://git.kernel.org/stable/c/9ffc602e14d7b9f7e7cb2f67e18dfef9ef8af676
• https://git.kernel.org/stable/c/b5a3bb7f6f164eb6ee74ef4898dcd019b2063448