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

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Message-ID: <aRQyMck_MeVvvCdX@infradead.org>
Date: Tue, 11 Nov 2025 23:07:29 -0800
From: Christoph Hellwig <hch@...radead.org>
To: Uladzislau Rezki <urezki@...il.com>
Cc: syzbot ci <syzbot+ci9989da8336cb2bc7@...kaller.appspotmail.com>,
	akpm@...ux-foundation.org, hch@...radead.org, hch@....de,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	vishal.moola@...il.com, syzbot@...ts.linux.dev,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot ci] Re: make vmalloc gfp flags usage more apparent

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.