Re: [PATCH v2 2/6] smb: clear the aes_cmac_key and aes_cmac_ctx when done

[Thomas Huth]

On 11/08/2026 12.31, Namjae Jeon wrote:
> > diff --git a/fs/smb/client/smb2transport.c b/fs/smb/client/smb2transport.c
> > index 1143ee52470a7..d23566da2ac81 100644
> > --- a/fs/smb/client/smb2transport.c
> > +++ b/fs/smb/client/smb2transport.c
> > @@ -464,8 +464,8 @@ smb3_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
> >          unsigned char smb3_signature[SMB2_CMACAES_SIZE];
> >          struct kvec *iov = rqst->rq_iov;
> >          struct smb2_hdr *shdr = (struct smb2_hdr *)iov[0].iov_base;
> > -       struct aes_cmac_key cmac_key;
> > -       struct aes_cmac_ctx cmac_ctx;
> > +       struct aes_cmac_key cmac_key __cleanup(aes_cmac_zeroize_key);
> > +       struct aes_cmac_ctx cmac_ctx __cleanup(aes_cmac_zeroize_ctx);
> >          struct smb_rqst drqst;
> >          u8 key[SMB3_SIGN_KEY_SIZE];
> Shouldn’t we also clear the raw key with memzero_explicit(key,
> sizeof(key)) immediately after aes_cmac_preparekey() ?
>
>          rc = aes_cmac_preparekey(&cmac_key, key, SMB2_CMACAES_SIZE);
> +        memzero_explicit(key, sizeof(key));
>          if (rc) {
>                  cifs_server_dbg(VFS, "%s: Could not set key for cmac
> aes\n", __func__);
>                  return rc;
>          }
Yes, but I was planning to do all the scrubbing for such other spots in a 
separate patch series (similar to what I've posted for the smb/server code 
already) ... this patch series here focuses on aes_cmac_zeroize_key and 
aes_cmac_zeroize_ctx only. I hope that's ok?

 Thomas