On Mon, Oct 21, 2019 at 03:11:49PM +0200, Peter Zijlstra wrote:
> On Mon, Oct 21, 2019 at 02:35:49PM +0200, Peter Zijlstra wrote:
> > On Fri, Oct 18, 2019 at 08:33:11AM -0700, Randy Dunlap wrote:
> > > On 10/18/19 12:03 AM, Stephen Rothwell wrote:
> > > > Hi all,
> > > >
> > > > Changes since 20191017:
> > > >
> > >
> > > on x86_64:
> > > lib/usercopy.o: warning: objtool: check_zeroed_user()+0x35f: call to __ubsan_handle_shift_out_of_bounds() with UACCESS enabled
> >
> > Blergh... I suppose the below will fix that. I'm a bit conflicted on it
> > though, the alternative is annotating more ubsan crud.
>
> By popular request; here's that alternative. Completely untested :-)
Am I not getting some mails? :)
I prefer this one as it allows us to avoid working around this in
usercopy.c. Should especially make if this potentially helps in other
cases as well?
>
> ---
> lib/ubsan.c | 5 ++++-
> tools/objtool/check.c | 1 +
> 2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/lib/ubsan.c b/lib/ubsan.c
> index 39d5952c4273..0dce3ff45b5b 100644
> --- a/lib/ubsan.c
> +++ b/lib/ubsan.c
> @@ -359,9 +359,10 @@ void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
> struct type_descriptor *lhs_type = data->lhs_type;
> char rhs_str[VALUE_LENGTH];
> char lhs_str[VALUE_LENGTH];
> + unsigned long flags = user_access_save();
>
> if (suppress_report(&data->location))
> - return;
> + goto out;
>
> ubsan_prologue(&data->location);
>
> @@ -387,6 +388,8 @@ void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
> lhs_type->type_name);
>
> ubsan_epilogue();
> +out:
> + user_access_restore(flags);
> }
> EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
>
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index 543c068096b1..4768d91c6d68 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -482,6 +482,7 @@ static const char *uaccess_safe_builtin[] = {
> "ubsan_type_mismatch_common",
> "__ubsan_handle_type_mismatch",
> "__ubsan_handle_type_mismatch_v1",
> + "__ubsan_handle_shift_out_of_bounds",
> /* misc */
> "csum_partial_copy_generic",
> "__memcpy_mcsafe",
