Re: [PATCH bpf-next v2 1/2] bpf: cpumap: propagate underlying error in cpu_map_update_elem()

Kohei Enju enjuk@amazon.com writes:

After commit 9216477449f3 ("bpf: cpumap: Add the possibility to attach an eBPF program to cpumap"), __cpu_map_entry_alloc() may fail with errors other than -ENOMEM, such as -EBADF or -EINVAL.

However, __cpu_map_entry_alloc() returns NULL on all failures, and cpu_map_update_elem() unconditionally converts this NULL into -ENOMEM. As a result, user space always receives -ENOMEM regardless of the actual underlying error.

Examples of unexpected behavior:

• Nonexistent fd : -ENOMEM (should be -EBADF)
• Non-BPF fd : -ENOMEM (should be -EINVAL)
• Bad attach type : -ENOMEM (should be -EINVAL)

Change __cpu_map_entry_alloc() to return ERR_PTR(err) instead of NULL and have cpu_map_update_elem() propagate this error.

Signed-off-by: Kohei Enju enjuk@amazon.com

Reviewed-by: Toke Høiland-Jørgensen toke@redhat.com