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 >
