CVE-2021-47265: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-47265 affects the Linux kernel's RDMA (Remote Direct Memory Access) subsystem. The vulnerability was discovered in the flow rule creation functionality where there was a missing port validation check in the mlx5_ib driver. This could lead to a system crash (oops) when creating RDMA flow rules (Kernel Git).

The vulnerability stems from insufficient validation of port values when creating flow rules in the RDMA subsystem. The issue specifically affected the mlx5_ib driver, where a missing validation check could trigger a kernel oops. The vulnerability was fixed by implementing proper port validation at the user input level and removing redundant validation checks in the drivers. The fix involved modifying the core RDMA code to validate port values using rdma_is_port_valid() before proceeding with flow rule creation (Kernel Git).

When exploited, this vulnerability could cause a kernel oops (system crash), potentially leading to denial of service conditions. The issue manifests during the creation of RDMA flow rules, affecting system stability and availability (Kernel Git).

The vulnerability can be triggered through the RDMA userspace interface when creating flow rules with invalid port values. A proof of concept exists in the form of a call trace that demonstrates the crash sequence through the mlx5_ib driver (Kernel Git).

The issue has been fixed in the Linux kernel by implementing proper port validation in the RDMA core code. The fix involves adding a validation check using rdma_is_port_valid() in the ib_uverbs_ex_create_flow function and removing redundant checks from individual drivers. Users should update their Linux kernel to a version containing this fix (Kernel Git).