CVE-2021-47132: 
Linux Kernel vulnerability analysis and mitigation

In the Linux kernel, a vulnerability (CVE-2021-47132) was discovered in the MPTCP (Multipath TCP) implementation. The issue involves sk_forward_memory corruption during retransmission operations. The vulnerability stems from improper handling of the socket spin lock when updating the sk_forward_memory field (Kernel Commit).

The vulnerability occurs in the MPTCP implementation where the sk_forward_memory field is protected by the msk socket spin_lock rather than the standard socket lock. A code path in __mptcp_retrans() -> __mptcp_clean_una_wakeup() updates this field without properly handling the relevant lock. Several helpers in __mptcp_clean_una_wakeup() update sk_forward_alloc without proper locking, potentially causing memory corruption (Kernel Commit).

The vulnerability could lead to memory corruption in the Linux kernel's MPTCP implementation, potentially affecting system stability and security (Kernel Commit).

The vulnerability requires access to a system running MPTCP and the ability to trigger retransmission operations. No public exploits have been identified (Kernel Commit).

The issue has been fixed by introducing a new variant of the affected function that explicitly acquires the msk spin lock. The fix was implemented in the Linux kernel through commit b5941f066b4ca331db225a976dae1d6ca8cf0ae3 (Kernel Commit).