CVE-2024-50269

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

usb: musb: sunxi: Fix accessing an released usb phy

Commit 6ed05c68cbca (usb: musb: sunxi: Explicitly release USB PHY on exit) will cause that usb phy @glue->xceiv is accessed after released.

1. register platform driver @sunxi_musb_driver // get the usb phy @glue->xceiv sunxi_musb_probe() -> devm_usb_get_phy().

2. register and unregister platform driver @musb_driver musb_probe() -> sunxi_musb_init() use the phy here //the phy is released here musb_remove() -> sunxi_musb_exit() -> devm_usb_put_phy()

3. register @musb_driver again musb_probe() -> sunxi_musb_init() use the phy here but the phy has been released at 2). …

Fixed by reverting the commit, namely, removing devm_usb_put_phy() from sunxi_musb_exit().

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/498dbd9aea205db9da674994b74c7bf8e18448bd
• https://git.kernel.org/stable/c/4aa77d5ea9944468e16c3eed15e858fd5de44de1
• https://git.kernel.org/stable/c/63559ba8077cbadae1c92a65b73ea522bf377dd9
• https://git.kernel.org/stable/c/6e2848d1c8c0139161e69ac0a94133e90e9988e8
• https://git.kernel.org/stable/c/721ddad945596220c123eb6f7126729fe277ee4f
• https://git.kernel.org/stable/c/8a30da5aa9609663b3e05bcc91a916537f66a4cd
• https://git.kernel.org/stable/c/b08baa75b989cf779cbfa0969681f8ba2dc46569
• https://git.kernel.org/stable/c/ccd811c304d2ee56189bfbc49302cb3c44361893