Re: [Kernel Bug] KASAN: slab-use-after-free Read in filemap_free_folio

[Matthew Wilcox]

On Mon, Feb 02, 2026 at 02:20:50PM +0800, 李龙兴 wrote:
> Dear Linux kernel developers and maintainers,
> 
> We would like to report a new kernel bug found by our tool. KASAN:

Don't be syzbot.  Get your changes into syzkaller upstream and let
syzbot do its thing.

> Allocated by task 49607:
>  kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
>  kasan_save_track+0x14/0x30 mm/kasan/common.c:77
>  unpoison_slab_object mm/kasan/common.c:342 [inline]
>  __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:368
>  kasan_slab_alloc include/linux/kasan.h:252 [inline]
>  slab_post_alloc_hook mm/slub.c:4978 [inline]
>  slab_alloc_node mm/slub.c:5288 [inline]
>  kmem_cache_alloc_lru_noprof+0x254/0x6e0 mm/slub.c:5307
>  ext4_alloc_inode+0x28/0x610 fs/ext4/super.c:1393

I'd suggest this is an ext4 problem, not a pagecache problem.

syzbot has good heuristics for this kind of thing now.  You don't.