For some reason arm64's Poly1305 code got changed to ignore the padbit
argument. As a result, the output is incorrect when the message length
is not a multiple of 16 (which is not reached with the standard
ChaCha20Poly1305, but bcachefs could reach this). Fix this.
Fixes: a59e5468a9 ("crypto: arm64/poly1305 - Add block-only interface")
Reported-by: Kent Overstreet <kent.overstreet@linux.dev>
Tested-by: Kent Overstreet <kent.overstreet@linux.dev>
Link: https://lore.kernel.org/r/20250616010654.367302-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
9d4204a810