Re: [PATCH v2] mm/codetag: clear tags before swap
From: Suren Baghdasaryan
Date: Thu Dec 12 2024 - 18:18:19 EST
On Thu, Dec 12, 2024 at 12:29 AM David Wang <00107082@xxxxxxx> wrote:
>
> When CONFIG_MEM_ALLOC_PROFILING_DEBUG is set, kernel WARN would be
> triggered when calling __alloc_tag_ref_set() during swap:
>
> alloc_tag was not cleared (got tag for mm/filemap.c:1951)
> WARNING: CPU: 0 PID: 816 at ./include/linux/alloc_tag.h...
>
> Clear code tags before swap can fix the warning. And this patch also fix
> a potential invalid address dereference in alloc_tag_add_check() when
> CONFIG_MEM_ALLOC_PROFILING_DEBUG is set and ref->ct is CODETAG_EMPTY,
> which is defined as ((void *)1).
>
> Signed-off-by: David Wang <00107082@xxxxxxx>
> Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> Closes: https://lore.kernel.org/oe-lkp/202412112227.df61ebb-lkp@xxxxxxxxx
> Suggested-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
I didn't really suggest much in this patch, so please replace above
Suggested-by with:
Acked-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Thanks for fixing this!
> ---
> include/linux/alloc_tag.h | 2 +-
> lib/alloc_tag.c | 7 +++++++
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
> index 7c0786bdf9af..cba024bf2db3 100644
> --- a/include/linux/alloc_tag.h
> +++ b/include/linux/alloc_tag.h
> @@ -135,7 +135,7 @@ static inline struct alloc_tag_counters alloc_tag_read(struct alloc_tag *tag)
> #ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
> static inline void alloc_tag_add_check(union codetag_ref *ref, struct alloc_tag *tag)
> {
> - WARN_ONCE(ref && ref->ct,
> + WARN_ONCE(ref && ref->ct && !is_codetag_empty(ref),
> "alloc_tag was not cleared (got tag for %s:%u)\n",
> ref->ct->filename, ref->ct->lineno);
>
> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> index 35f7560a309a..3a0413462e9f 100644
> --- a/lib/alloc_tag.c
> +++ b/lib/alloc_tag.c
> @@ -209,6 +209,13 @@ void pgalloc_tag_swap(struct folio *new, struct folio *old)
> return;
> }
>
> + /*
> + * Clear tag references to avoid debug warning when using
> + * __alloc_tag_ref_set() with non-empty reference.
> + */
> + set_codetag_empty(&ref_old);
> + set_codetag_empty(&ref_new);
> +
> /* swap tags */
> __alloc_tag_ref_set(&ref_old, tag_new);
> update_page_tag_ref(handle_old, &ref_old);
> --
> 2.39.2
>