bpf: Implement signature verification for BPF programs

This patch extends the BPF_PROG_LOAD command by adding three new fields
to `union bpf_attr` in the user-space API:

  - signature: A pointer to the signature blob.
  - signature_size: The size of the signature blob.
  - keyring_id: The serial number of a loaded kernel keyring (e.g.,
    the user or session keyring) containing the trusted public keys.

When a BPF program is loaded with a signature, the kernel:

1.  Retrieves the trusted keyring using the provided `keyring_id`.
2.  Verifies the supplied signature against the BPF program's
    instruction buffer.
3.  If the signature is valid and was generated by a key in the trusted
    keyring, the program load proceeds.
4.  If no signature is provided, the load proceeds as before, allowing
    for backward compatibility. LSMs can chose to restrict unsigned
    programs and implement a security policy.
5.  If signature verification fails for any reason,
    the program is not loaded.

Tested-by: syzbot@syzkaller.appspotmail.com
Signed-off-by: KP Singh <kpsingh@kernel.org>
Link: https://lore.kernel.org/r/20250921160120.9711-2-kpsingh@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index ef4ede8bb74f..969f63f8ca28 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -3898,7 +3898,7 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_p,
 
 	return verify_pkcs7_signature(data, data_len, sig, sig_len,
 				      trusted_keyring->key,
-				      VERIFYING_UNSPECIFIED_SIGNATURE, NULL,
+				      VERIFYING_BPF_SIGNATURE, NULL,
 				      NULL);
 #else
 	return -EOPNOTSUPP;