CVE-2024-26800

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

tls: fix use-after-free on failed backlog decryption

When the decrypt request goes to the backlog and crypto_aead_decrypt returns -EBUSY, tls_do_decryption will wait until all async decryptions have completed. If one of them fails, tls_do_decryption will return -EBADMSG and tls_decrypt_sg jumps to the error path, releasing all the pages. But the pages have been passed to the async callback, and have already been released by tls_decrypt_done.

The only true async case is when crypto_aead_decrypt returns -EINPROGRESS. With -EBUSY, we already waited so we can tell tls_sw_recvmsg that the data is available for immediate copy, but we need to notify tls_decrypt_sg (via the new ->async_done flag) that the memory has already been released.

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/13114dc5543069f7b97991e3b79937b6da05f5b0
• https://git.kernel.org/stable/c/1ac9fb84bc7ecd4bc6428118301d9d864d2a58d1
• https://git.kernel.org/stable/c/81be85353b0f5a7b660635634b655329b429eefe
• https://git.kernel.org/stable/c/f2b85a4cc763841843de693bbd7308fe9a2c4c89
• https://git.kernel.org/stable/c/13114dc5543069f7b97991e3b79937b6da05f5b0
• https://git.kernel.org/stable/c/1ac9fb84bc7ecd4bc6428118301d9d864d2a58d1
• https://git.kernel.org/stable/c/81be85353b0f5a7b660635634b655329b429eefe
• https://git.kernel.org/stable/c/f2b85a4cc763841843de693bbd7308fe9a2c4c89