CVE-2024-35986

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

phy: ti: tusb1210: Resolve charger-det crash if charger psy is unregistered

The power_supply frame-work is not really designed for there to be long living in kernel references to power_supply devices.

Specifically unregistering a power_supply while some other code has a reference to it triggers a WARN in power_supply_unregister():

WARN_ON(atomic_dec_return(&psy->use_cnt));

Folllowed by the power_supply still getting removed and the backing data freed anyway, leaving the tusb1210 charger-detect code with a dangling reference, resulting in a crash the next time tusb1210_get_online() is called.

Fix this by only holding the reference in tusb1210_get_online() freeing it at the end of the function. Note this still leaves a theoretical race window, but it avoids the issue when manually rmmod-ing the charger chip driver during development.

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/25b3498485ac281e5851700e33b97f12c9533fd8
• https://git.kernel.org/stable/c/73224a5d2180066c7fe05b4656647601ba08d588
• https://git.kernel.org/stable/c/9827caa5105fb16d1fae2e75c8d0e4662014b3ca
• https://git.kernel.org/stable/c/bf6e4ee5c43690e4c5a8a057bbcd4ff986bed052
• https://git.kernel.org/stable/c/25b3498485ac281e5851700e33b97f12c9533fd8
• https://git.kernel.org/stable/c/73224a5d2180066c7fe05b4656647601ba08d588
• https://git.kernel.org/stable/c/9827caa5105fb16d1fae2e75c8d0e4662014b3ca
• https://git.kernel.org/stable/c/bf6e4ee5c43690e4c5a8a057bbcd4ff986bed052