CVE-2025-38502

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

bpf: Fix oob access in cgroup local storage

Lonial reported that an out-of-bounds access in cgroup local storage

can be crafted via tail calls. Given two programs each utilizing a

cgroup local storage with a different value size, and one program

doing a tail call into the other. The verifier will validate each of

the indivial programs just fine. However, in the runtime context

the bpf_cg_run_ctx holds an bpf_prog_array_item which contains the

BPF program as well as any cgroup local storage flavor the program

uses. Helpers such as bpf_get_local_storage() pick this up from the

runtime context:

ctx = container_of(current->bpf_ctx, struct bpf_cg_run_ctx, run_ctx);

storage = ctx->prog_item->cgroup_storage[stype];

if (stype == BPF_CGROUP_STORAGE_SHARED)

ptr = &READ_ONCE(storage->buf)->data[0];

else

ptr = this_cpu_ptr(storage->percpu_buf);

For the second program which was called from the originally attached

one, this means bpf_get_local_storage() will pick up the former

program's map, not its own. With mismatching sizes, this can result

in an unintended out-of-bounds access.

To fix this issue, we need to extend bpf_map_owner with an array of

storage_cookie[] to match on i) the exact maps from the original

program if the second program was using bpf_get_local_storage(), or

ii) allow the tail call combination if the second program was not

using any of the cgroup local storage maps.