Re: [syzbot ci] Re: make vmalloc gfp flags usage more apparent

Uladzislau Rezki
2025-11-12T12:02:08Z

On Tue, Nov 11, 2025 at 11:07:29PM -0800, Christoph Hellwig wrote:
> On Tue, Nov 11, 2025 at 09:21:06PM +0100, Uladzislau Rezki wrote:
> > > Unexpected gfp: 0x100000 (__GFP_HARDWALL). Fixing up to gfp: 0xdc0 (GFP_KERNEL|__GFP_ZERO). Fix your code!
> > >
> > It looks like we need to add __GFP_HARDWALL to the white-list-mask.
>
> __GFP_HARDWALL is part of GFP_USER. Doing GFP_USER vmalloc sounds like
> a bit of an odd idea to me, but there are a few users mostly in bpf
> and drm code (why do these always show up for odd API usage patterns?).
>
> So I guess yes, we'll need to allow it for now, but I'd like to start
> a discussion if it really makes much sense.
>
<snip>
/* plain bpf_prog allocation */
prog = bpf_prog_alloc(bpf_prog_size(attr->insn_cnt), GFP_USER);
if (!prog) {
<snip>

I assume that was the place that triggered the splat.

Vishal, will you send the patch adding GFP_USER to address the splat?

--
Uladzislau Rezki