Commit 640a6039 authored by David Wang's avatar David Wang Committed by Andrew Morton
Browse files

mm/codetag: clear tags before swap 

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: 51f43d5d ("mm/codetag: swap tags when migrate pages")
Signed-off-by: default avatarDavid Wang <00107082@163.com>
Reported-by: default avatarkernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202412112227.df61ebb-lkp@intel.com


Acked-by: default avatarSuren 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 30c2de0a

include/linux/alloc_tag.h

+1 −1
Original line number Diff line number Diff line
@@ -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);

lib/alloc_tag.c

+7 −0
Original line number Diff line number Diff line
@@ -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);