+ mm-codetag-clear-tags-before-swap.patch added to mm-hotfixes-unstable branch - Linux-stable-mirror

13 Dec 2024

The patch titled
     Subject: mm/codetag: clear tags before swap
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-codetag-clear-tags-before-swap.patch
This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
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branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: David Wang 00107082@163.com
Subject: mm/codetag: clear tags before swap
Date: Fri, 13 Dec 2024 09:33:32 +0800
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: 51f43d5d82ed ("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
---
include/linux/alloc_tag.h |    2 +-
 lib/alloc_tag.c           |    7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

--- a/include/linux/alloc_tag.h~mm-codetag-clear-tags-before-swap
+++ a/include/linux/alloc_tag.h
@@ -140,7 +140,7 @@ static inline struct alloc_tag_counters
 #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);
--- a/lib/alloc_tag.c~mm-codetag-clear-tags-before-swap
+++ a/lib/alloc_tag.c
@@ -209,6 +209,13 @@ void pgalloc_tag_swap(struct folio *new,
    	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);
_
Patches currently in -mm which might be from 00107082@163.com are
mm-codetag-clear-tags-before-swap.patch

    