Null Pointer Dereference in Linux Kernel TTY Affects MUX Activation

CVE-2022-49940

What is CVE-2022-49940?

A null pointer dereference vulnerability exists in the Linux kernel TTY subsystem, specifically within the 'gsm_receive_buf()' function. This issue arises when the 'gsm->receive()' function is invoked without proper initialization of the MUX, leading to a potential crash. The vulnerability occurs when the code incorrectly assumes it is safe to call 'gsm->receive()' after MUX activation, allowing access to this function without prior configuration. To mitigate this risk, a sanity check has been introduced to ensure that 'gsm->receive()' is only called when it has been initialized, thereby preventing the null pointer dereference.

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