Re: [PATCH 3/3] module: Add compile-time check for embedded NUL characters

Luck, Tony
2025-12-10T22:29:56Z

[Added Dan Carpenter and Chris Li]

Dan and Chris,

You're in the git log for sparse wrting/commiting fixes. Can you take
a look at this? Sami's fix works for me.

-Tony

On Wed, Dec 10, 2025 at 01:00:20AM +0000, Sami Tolvanen wrote:
> On Tue, Dec 09, 2025 at 10:29:06AM -0800, Luck, Tony wrote:
> > On Tue, Dec 09, 2025 at 08:45:14AM -0800, Luck, Tony wrote:
> > > On Tue, Dec 09, 2025 at 04:20:06PM +0000, Luck, Tony wrote:
> > > > >> Likewise, I just got the following kernel test robot report sent to me,
> > > > >> where it's warning about MODULE_LICENSE("GPL"):
> > > > >> https://lore.kernel.org/all/202512090359.7BkUaiC9-lkp@intel.com/
> > > > >
> > > > > Can you both confirm which version of sparse are you using?
> > > > >
> > > > > My understanding was that this patch fixed that problem:
> > > > > >https://lore.kernel.org/linux-sparse/CACePvbVG2KrGQq4cNKV=wbO5h=jp3M0RO1SdfX8kV4OukjPG8A@mail.gmail.com/T/#mf838b3e2e3245d88c30a801ea7473d5a5c0eb121
> > > >
> > > > > The patch is already merged into the sparse tree, and I was not able to
> > > > > reproduce the issue.
> > > >
> > > > I pulled the latest sparse source and re-checked before reporting. Top commit I have is the one you mention:
> > > >
> > > > fbdde3127b83 ("builtin: implement __builtin_strlen() for constants")
> > > >
> > > > I'm building latest Linus tree from the current merge window (well latest as-of yesterday):
> > > >
> > > > c2f2b01b74be ("Merge tag 'i3c/for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux")
> > >
> > > I added a debug trace to the new expand_strlen() function added to
> > > sparse. It is being called and doing the right thing. My trace says:
> > >
> > > len(GPL) = 3
> >
> > Simple test case:
> >
> > $ cat -n s.c
> > 1
> > 2 _Static_assert(sizeof("GPL") - 1 == 3, "sizeof");
> > 3
> > 4 _Static_assert(__builtin_strlen("GPL") == 3, "strlen");
> >
> > $ sparse s.c
> > s.c:4:40: error: bad integer constant expression
> > s.c:4:40: error: static assertion failed: "strlen"
> >
> > So the "sizeof" bit is OK. But the __builtin_strlen() isn't.
>
> This looks like a bug in Sparse. The CEF_ICE flag isn't propagated to
> the comparison expression, which it presumably should be when both
> sides are integer constant expressions.
>
> I'm not really familiar enough with Sparse to know whether this is the
> correct place to handle this case, but this quick hack fixes the issue
> for me:
>
> diff --git a/expand.c b/expand.c
> index f14e7181..71221d35 100644
> --- a/expand.c
> +++ b/expand.c
> @@ -535,6 +535,8 @@ static int expand_compare(struct expression *expr)
> expr->taint = 0;
> return 0;
> }
> + if (left->flags & CEF_ICE && right->flags & CEF_ICE)
> + expr->flags |= CEF_SET_ICE;
> if (simplify_cmp_binop(expr, left->ctype))
> return 0;
> if (simplify_float_cmp(expr, left->ctype))
>
> Sami