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

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Message-ID: <aRXeK_C44xGb3ovg@milan>
Date: Thu, 13 Nov 2025 14:33:31 +0100
From: Uladzislau Rezki <urezki@...il.com>
To: vishal.moola@...il.com
Cc: akpm@...ux-foundation.org, bpf@...r.kernel.org, hch@...radead.org,
	hch@....de, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	urezki@...il.com, 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 Wed, Nov 12, 2025 at 11:41:37PM -0800, syzbot ci wrote:
> syzbot ci has tested the following series
> 
> [v2] make vmalloc gfp flags usage more apparent
> https://lore.kernel.org/all/20251112185834.32487-1-vishal.moola@gmail.com
> * [PATCH v2 1/4] mm/vmalloc: warn on invalid vmalloc gfp flags
> * [PATCH v2 2/4] mm/vmalloc: Add a helper to optimize vmalloc allocation gfps
> * [PATCH v2 3/4] mm/vmalloc: cleanup large_gfp in vm_area_alloc_pages()
> * [PATCH v2 4/4] mm/vmalloc: cleanup gfp flag use in new_vmap_block()
> 
> and found the following issue:
> WARNING: kmalloc bug in bpf_prog_alloc_no_stats
> 
> Full report is available here:
> https://ci.syzbot.org/series/46d6cb1a-188d-4ff5-8fab-9c58465d74d3
> 
> ***
> 
> WARNING: kmalloc bug in bpf_prog_alloc_no_stats
> 
> tree:      linux-next
> URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next
> base:      b179ce312bafcb8c68dc718e015aee79b7939ff0
> arch:      amd64
> compiler:  Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> config:    https://ci.syzbot.org/builds/3449e2a5-35e0-4eac-86c6-97ca0ec741d7/config
> 
> ------------[ cut here ]------------
> Unexpected gfp: 0x400000 (__GFP_ACCOUNT). Fixing up to gfp: 0xdc0 (GFP_KERNEL|__GFP_ZERO). Fix your code!
> WARNING: mm/vmalloc.c:3938 at vmalloc_fix_flags+0x9c/0xe0, CPU#1: syz-executor/6079
> Modules linked in:
>
Again bpf :)

GFP_KERNEL_ACCOUNT? I saw there have been __GFP_HARDWALL added already,
IMO it is worth to replace it by "high level flag", which is GFP_USER.

--
Uladzislau Rezki