nvmet-auth: zero the AUTH_RECEIVE response buffer

commit 3ddcfb0 upstream.

nvmet_execute_auth_receive() allocates the response buffer with kmalloc()
sized by the host-supplied AUTH_RECEIVE allocation length, but the
DH-HMAC-CHAP builders write only a fixed-size message into it. The full
allocation length is then copied to the wire by nvmet_copy_to_sgl(), so a
remote initiator receives the bytes past the built message -- up to nearly
a page of uninitialized slab -- during the pre-authentication handshake.

Allocate the buffer with kzalloc() so the unwritten tail is zeroed before
it is sent; conforming responses are unaffected.

Fixes: db1312d ("nvmet: implement basic In-Band Authentication")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: bryamzxz

drivers/nvme/target/fabrics-cmd-auth.c

@@ -469,7 +469,7 @@ void nvmet_execute_auth_receive(struct nvmet_req *req)
 		return;
 	}
 
-	d = kmalloc(al, GFP_KERNEL);
+	d = kzalloc(al, GFP_KERNEL);
 	if (!d) {
 		status = NVME_SC_INTERNAL;
 		goto done;