Re: [PATCH v2] fs/buffer: add alert in try_to_free_buffers() for folios without buffers
From: Matthew Wilcox
Date: Mon Dec 15 2025 - 09:10:10 EST
On Mon, Dec 15, 2025 at 03:07:35PM +0100, Christian Brauner wrote:
> On Thu, 11 Dec 2025 18:42:11 +0530, Deepakkumar Karn wrote:
> > try_to_free_buffers() can be called on folios with no buffers attached
> > when filemap_release_folio() is invoked on a folio belonging to a mapping
> > with AS_RELEASE_ALWAYS set but no release_folio operation defined.
> >
> > In such cases, folio_needs_release() returns true because of the
> > AS_RELEASE_ALWAYS flag, but the folio has no private buffer data. This
> > causes try_to_free_buffers() to call drop_buffers() on a folio with no
> > buffers, leading to a null pointer dereference.
> >
> > [...]
>
> Applied to the vfs-7.0.misc branch of the vfs/vfs.git tree.
> Patches in the vfs-7.0.misc branch should appear in linux-next soon.
No, this is the wrong fix. Please drop.