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If obj_exts allocation failed, slab->obj_exts is set to OBJEXTS_ALLOC_FAIL, But we do not clear it when freeing the slab. Since OBJEXTS_ALLOC_FAIL and MEMCG_DATA_OBJEXTS currently share the same bit position, during the release of the associated folio, a VM_BUG_ON_FOLIO() check in folio_memcg_kmem() is triggered because the OBJEXTS_ALLOC_FAIL flag was not cleared, causing it to be interpreted as a kmem folio (non-slab) with MEMCG_OBJEXTS_DATA flag set, which is invalid because MEMCG_OBJEXTS_DATA is supposed to be set only on slabs. Another problem that predates sharing the OBJEXTS_ALLOC_FAIL and MEMCG_DATA_OBJEXTS bits is that on configurations with is_check_pages_enabled(), the non-cleared bit in page->memcg_data will trigger a free_page_is_bad() failure "page still charged to cgroup" When freeing a slab, we clear slab->obj_exts if the obj_ext array has been successfully allocated. So let's clear it also when the allocation has failed. Fixes:09c46563ff("codetag: debug: introduce OBJEXTS_ALLOC_FAIL to mark failed slab_ext allocations") Fixes:7612833192("slab: Reuse first bit for OBJEXTS_ALLOC_FAIL") Link: https://lore.kernel.org/all/20251015141642.700170-1-hao.ge@linux.dev/ Cc: <stable@vger.kernel.org> Signed-off-by: Hao Ge <gehao@kylinos.cn> Reviewed-by: Suren Baghdasaryan <surenb@google.com> Reviewed-by: Harry Yoo <harry.yoo@oracle.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.