From 0ae0227fa31dda5bfc6b5a0145952d46fe57408b Mon Sep 17 00:00:00 2001 From: David Wang <00107082@163.com> Date: Tue, 6 May 2025 03:30:34 +0800 Subject: [PATCH] mm/codetag: move tag retrieval back upfront in __free_pages() Commit 51ff4d7486f0 ("mm: avoid extra mem_alloc_profiling_enabled() checks") introduces a possible use-after-free scenario, when page is non-compound, page[0] could be released by other thread right after put_page_testzero failed in current thread, pgalloc_tag_sub_pages afterwards would manipulate an invalid page for accounting remaining pages: [timeline] [thread1] [thread2] | alloc_page non-compound V | get_page, rf counter inc V | in ___free_pages | put_page_testzero fails V | put_page, page released V | in ___free_pages, | pgalloc_tag_sub_pages | manipulate an invalid page V Restore __free_pages() to its state before, retrieve alloc tag beforehand. Link: https://lkml.kernel.org/r/20250505193034.91682-1-00107082@163.com Fixes: 51ff4d7486f0 ("mm: avoid extra mem_alloc_profiling_enabled() checks") Signed-off-by: David Wang <00107082@163.com> Acked-by: Suren Baghdasaryan Reviewed-by: Vlastimil Babka Cc: Brendan Jackman Cc: Johannes Weiner Cc: Michal Hocko Cc: Shakeel Butt Cc: Vlastimil Babka Cc: Zi Yan Signed-off-by: Andrew Morton --- include/linux/pgalloc_tag.h | 8 ++++++++ mm/page_alloc.c | 15 ++++++--------- 2 files changed, 14 insertions(+), 9 deletions(-) diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h index c74077977830..8a7f4f802c57 100644 --- a/include/linux/pgalloc_tag.h +++ b/include/linux/pgalloc_tag.h @@ -188,6 +188,13 @@ static inline struct alloc_tag *__pgalloc_tag_get(struct page *page) return tag; } +static inline struct alloc_tag *pgalloc_tag_get(struct page *page) +{ + if (mem_alloc_profiling_enabled()) + return __pgalloc_tag_get(page); + return NULL; +} + void pgalloc_tag_split(struct folio *folio, int old_order, int new_order); void pgalloc_tag_swap(struct folio *new, struct folio *old); @@ -199,6 +206,7 @@ static inline void clear_page_tag_ref(struct page *page) {} static inline void alloc_tag_sec_init(void) {} static inline void pgalloc_tag_split(struct folio *folio, int old_order, int new_order) {} static inline void pgalloc_tag_swap(struct folio *new, struct folio *old) {} +static inline struct alloc_tag *pgalloc_tag_get(struct page *page) { return NULL; } #endif /* CONFIG_MEM_ALLOC_PROFILING */ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 5669baf2a6fe..1b00e14a9780 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1151,14 +1151,9 @@ static inline void pgalloc_tag_sub(struct page *page, unsigned int nr) __pgalloc_tag_sub(page, nr); } -static inline void pgalloc_tag_sub_pages(struct page *page, unsigned int nr) +/* When tag is not NULL, assuming mem_alloc_profiling_enabled */ +static inline void pgalloc_tag_sub_pages(struct alloc_tag *tag, unsigned int nr) { - struct alloc_tag *tag; - - if (!mem_alloc_profiling_enabled()) - return; - - tag = __pgalloc_tag_get(page); if (tag) this_cpu_sub(tag->counters->bytes, PAGE_SIZE * nr); } @@ -1168,7 +1163,7 @@ static inline void pgalloc_tag_sub_pages(struct page *page, unsigned int nr) static inline void pgalloc_tag_add(struct page *page, struct task_struct *task, unsigned int nr) {} static inline void pgalloc_tag_sub(struct page *page, unsigned int nr) {} -static inline void pgalloc_tag_sub_pages(struct page *page, unsigned int nr) {} +static inline void pgalloc_tag_sub_pages(struct alloc_tag *tag, unsigned int nr) {} #endif /* CONFIG_MEM_ALLOC_PROFILING */ @@ -5065,11 +5060,13 @@ static void ___free_pages(struct page *page, unsigned int order, { /* get PageHead before we drop reference */ int head = PageHead(page); + /* get alloc tag in case the page is released by others */ + struct alloc_tag *tag = pgalloc_tag_get(page); if (put_page_testzero(page)) __free_frozen_pages(page, order, fpi_flags); else if (!head) { - pgalloc_tag_sub_pages(page, (1 << order) - 1); + pgalloc_tag_sub_pages(tag, (1 << order) - 1); while (order-- > 0) __free_frozen_pages(page + (1 << order), order, fpi_flags);