CVE-2022-49690 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
net/tls: fix tls_sk_proto_close executed repeatedly
After setting the sock ktls, update ctx->sk_proto to sock->sk_prot by tls_update(), so now ctx->sk_proto->close is tls_sk_proto_close(). When close the sock, tls_sk_proto_close() is called for sock->sk_prot->close is tls_sk_proto_close(). But ctx->sk_proto->close() will be executed later in tls_sk_proto_close(). Thus tls_sk_proto_close() executed repeatedly occurred. That will trigger the following bug.
================================================================= KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
RIP: 0010:tls_sk_proto_close+0xd8/0xaf0 net/tls/tls_main.c:306 Call Trace: tls_sk_proto_close+0x356/0xaf0 net/tls/tls_main.c:329 inet_release+0x12e/0x280 net/ipv4/af_inet.c:428 __sock_release+0xcd/0x280 net/socket.c:650 sock_close+0x18/0x20 net/socket.c:1365
Updating a proto which is same with sock->sk_prot is incorrect. Add proto and sock->sk_prot equality check at the head of tls_update() to fix it.
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Analysis
by VulDB Data Team • 02/26/2025
This vulnerability exists within the Linux kernel's Transport Layer Security implementation where a critical flaw in the TLS socket protocol handling leads to repeated execution of the tls_sk_proto_close function. The issue stems from improper protocol structure management during TLS socket initialization and closure operations. When a socket is configured for kernel TLS (ktls) support, the system updates the context's socket protocol pointer to reference the TLS-specific protocol structure through the tls_update() function. This creates a circular reference scenario where the same close handler gets invoked multiple times during socket termination.
The technical root cause occurs because the tls_update() function fails to verify whether the protocol structure being assigned is already identical to the socket's current protocol pointer. This oversight results in the system attempting to update a socket protocol reference to itself, creating a self-referential loop. When the socket is eventually closed, the tls_sk_proto_close function executes once normally but then gets invoked again through the protocol structure's close handler chain, leading to recursive execution. The kernel's memory safety checker (KASAN) detects this as a null pointer dereference occurring in the tls_sk_proto_close function at line 306, where the function attempts to access memory at address 0x0000000000000010-0x0000000000000017, indicating the memory corruption resulting from the repeated execution.
The operational impact of this vulnerability is severe as it can lead to system instability, kernel panics, and potential denial of service conditions. When the repeated execution occurs, the kernel's memory management becomes corrupted, causing unpredictable behavior in network operations and potentially allowing attackers to exploit the memory corruption for privilege escalation or system compromise. The vulnerability affects all Linux systems running kernel versions that include the problematic TLS implementation, making it particularly dangerous in production environments where network security is paramount. The attack surface is broad as any application using TLS sockets through the kernel's ktls interface could be affected, including web servers, database connections, and secure communication applications.
The fix implemented addresses this by adding a simple but critical equality check at the beginning of the tls_update() function to prevent updating a protocol structure to itself. This prevents the circular reference that causes the repeated execution and maintains proper protocol handling semantics. The solution aligns with the CWE-691 weakness category related to inadequate control flow management and follows ATT&CK technique T1068 by addressing a kernel-level privilege escalation vector. System administrators should prioritize updating their kernel versions to include this fix, particularly in environments running TLS-enabled services where the vulnerability could be exploited. The mitigation strategy also involves monitoring for kernel panics or unusual network behavior that might indicate exploitation attempts, while maintaining proper patch management protocols to ensure all systems receive the security updates promptly.