Bluetooth: Fix type of len in rfcomm_sock_getsockopt{,_old}()

Bluetooth: Fix type of len in rfcomm_sock_getsockopt{,_old}()

commit 5fe6caa62b07fd39cd6a28acc8f92ba2955e11a6 upstream.

Commit 9bf4e919ccad worked around an issue introduced after an innocuous
optimisation change in LLVM main:

> len is defined as an 'int' because it is assigned from
> '__user int *optlen'. However, it is clamped against the result of
> sizeof(), which has a type of 'size_t' ('unsigned long' for 64-bit
> platforms). This is done with min_t() because min() requires compatible
> types, which results in both len and the result of sizeof() being casted
> to 'unsigned int', meaning len changes signs and the result of sizeof()
> is truncated. From there, len is passed to copy_to_user(), which has a
> third parameter type of 'unsigned long', so it is widened and changes
> signs again. This excessive casting in combination with the KCSAN
> instrumentation causes LLVM to fail to eliminate the __bad_copy_from()
> call, failing the build.

The same issue occurs in rfcomm in functions rfcomm_sock_getsockopt and
rfcomm_sock_getsockopt_old.

Change the type of len to size_t in both rfcomm_sock_getsockopt and
rfcomm_sock_getsockopt_old and replace min_t() with min().

Cc: stable@vger.kernel.org
Co-authored-by: Aleksei Vetrov <vvvvvv@google.com>
Improves: 9bf4e919ccad ("Bluetooth: Fix type of len in {l2cap,sco}_sock_getsockopt_old()")
Link: https://github.com/ClangBuiltLinux/linux/issues/2007
Link: https://github.com/llvm/llvm-project/issues/85647
Signed-off-by: Andrej Shadura <andrew.shadura@collabora.co.uk>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>