Re: [PATCH v2] erofs: fix folio reuse from a different address_space in erofs_bread()

[Gao Xiang]

On Thu, Oct 01, 2026 at 03:19:01AM +0800, Binglei Wang wrote:
> erofs_bread() reuses a cached folio on page index match without
> checking folio->mapping.
> 
> xattr.c calls erofs_init_metabuf() twice on the same buffer without
> erofs_put_metabuf(); the two in_metabox sources differ, so buf->mapping
> can switch while buf->page still belongs to the old address_space.
> The next erofs_bread() then reads the wrong mapping, dropping shared
> xattrs with METABOX.
> 
> We require folio->mapping == buf->mapping in the reuse check; otherwise
> drop the cached folio and re-read via the slow path.
> 
> Fixes: 414091322c63 ("erofs: implement metadata compression")
> Cc: Bo Liu (OpenAnolis) <liubo03@xxxxxxxxxx>
> Signed-off-by: Binglei Wang <l3b2w1@xxxxxxxxx>

I have to tell you that the patch is still broken, and I failed to
apply like this:


Applying: erofs: fix folio reuse from a different address_space in erofs_bread()
Using index info to reconstruct a base tree...
error: patch failed: fs/erofs/data.c:33
error: fs/erofs/data.c: patch does not apply
error: Did you hand edit your patch?
It does not apply to blobs recorded in its index.
Patch failed at 0001 erofs: fix folio reuse from a different address_space in erofs_bread()


Could you just apply locally before sending out a version?
I could make a patch for you manually, but if you apply more patches
later, the broken email client should be fixed.

Thanks,
Gao Xiang