+ alloc_tag-fix-page_ext_get-page_ext_put-sequence-during-page-splitting.patch added to mm-unstable branch

+ alloc_tag-fix-page_ext_get-page_ext_put-sequence-during-page-splitting.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: alloc_tag: fix page_ext_get/page_ext_put sequence during page splitting
has been added to the -mm mm-unstable branch.  Its filename is
     alloc_tag-fix-page_ext_get-page_ext_put-sequence-during-page-splitting.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/alloc_tag-fix-page_ext_get-page_ext_put-sequence-during-page-splitting.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Suren Baghdasaryan <surenb@google.com>
Subject: alloc_tag: fix page_ext_get/page_ext_put sequence during page splitting
Date: Thu, 11 Jul 2024 15:04:57 -0700

pgalloc_tag_sub() might call page_ext_put() using a page different from
the one used in page_ext_get() call.  This does not pose an issue since
page_ext_put() ignores this parameter as long as it's non-NULL but
technically this is wrong.  Fix it by storing the original page used in
page_ext_get() and passing it to page_ext_put().

Link: https://lkml.kernel.org/r/20240711220457.1751071-3-surenb@google.com
Fixes: be25d1d4e822 ("mm: create new codetag references during page splitting")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/pgalloc_tag.h |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/include/linux/pgalloc_tag.h~alloc_tag-fix-page_ext_get-page_ext_put-sequence-during-page-splitting
+++ a/include/linux/pgalloc_tag.h
@@ -71,6 +71,7 @@ static inline void pgalloc_tag_sub(struc
 static inline void pgalloc_tag_split(struct page *page, unsigned int nr)
 {
 	int i;
+	struct page_ext *first_page_ext;
 	struct page_ext *page_ext;
 	union codetag_ref *ref;
 	struct alloc_tag *tag;
@@ -78,7 +79,7 @@ static inline void pgalloc_tag_split(str
 	if (!mem_alloc_profiling_enabled())
 		return;
 
-	page_ext = page_ext_get(page);
+	first_page_ext = page_ext = page_ext_get(page);
 	if (unlikely(!page_ext))
 		return;
 
@@ -94,7 +95,7 @@ static inline void pgalloc_tag_split(str
 		page_ext = page_ext_next(page_ext);
 	}
 out:
-	page_ext_put(page_ext);
+	page_ext_put(first_page_ext);
 }
 
 static inline struct alloc_tag *pgalloc_tag_get(struct page *page)
_

Patches currently in -mm which might be from surenb@google.com are

alloc_tag-export-memory-allocation-profiling-symbols-used-by-modules.patch
mm-add-comments-for-allocation-helpers-explaining-why-they-are-macros.patch
lib-add-missing-newline-character-in-the-warning-message.patch
lib-reuse-page_ext_data-to-obtain-codetag_ref.patch
alloc_tag-fix-page_ext_get-page_ext_put-sequence-during-page-splitting.patch