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mm/codetag: clear tags before swap

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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).

Link: https://lkml.kernel.org/r/20241213013332.89910-1-00107082@163.com
Fixes: 51f43d5d82 ("mm/codetag: swap tags when migrate pages")
Signed-off-by: David Wang <00107082@163.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202412112227.df61ebb-lkp@intel.com
Acked-by: Suren Baghdasaryan <surenb@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Yu Zhao <yuzhao@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Wang 2024-12-13 09:33:32 +08:00 committed by Andrew Morton
parent 30c2de0a26
commit 640a603943
2 changed files with 8 additions and 1 deletions
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2
include/linux/alloc_tag.h
View File

@ -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);

7
lib/alloc_tag.c
View File

@ -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);