CVE-2022-50219

/// Technical description

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

bpf: Fix KASAN use-after-free Read in compute_effective_progs

Syzbot found a Use After Free bug in compute_effective_progs().

The reproducer creates a number of BPF links, and causes a fault

injected alloc to fail, while calling bpf_link_detach on them.

Link detach triggers the link to be freed by bpf_link_free(),

which calls __cgroup_bpf_detach() and update_effective_progs().

If the memory allocation in this function fails, the function restores

the pointer to the bpf_cgroup_link on the cgroup list, but the memory

gets freed just after it returns. After this, every subsequent call to

update_effective_progs() causes this already deallocated pointer to be

dereferenced in prog_list_length(), and triggers KASAN UAF error.

To fix this issue don't preserve the pointer to the prog or link in the

list, but remove it and replace it with a dummy prog without shrinking

the table. The subsequent call to __cgroup_bpf_detach() o

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References