CVE-2026-52938 bpf: Fix NULL pointer dereference in bpf_sk_storage_clone and diag paths

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix NULL pointer dereference in bpfskstorageclone and diag paths bpfselemunlinknofail sets SDATAselem-smap to NULL before removing the selem from the storage hlist. A concurrent RCU reader in bpfskstorageclone can observe th...