From a273559e9eb68cb58c57803d76a1622b8324a878 Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Sat, 1 Jun 2024 16:38:40 -0700 Subject: lib/alloc_tag: fix RCU imbalance in pgalloc_tag_get() put_page_tag_ref() should be called only when get_page_tag_ref() returns a valid reference because only in that case get_page_tag_ref() enters RCU read section while put_page_tag_ref() will call rcu_read_unlock() even if the provided reference is NULL. Fix pgalloc_tag_get() which does not follow this rule causing RCU imbalance. Add a warning in put_page_tag_ref() to catch any future mistakes. Link: https://lkml.kernel.org/r/20240601233840.617458-1-surenb@google.com Fixes: cc92eba1c88b ("mm: fix non-compound multi-order memory accounting in __free_pages") Signed-off-by: Suren Baghdasaryan Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202405271029.6d2f9c4c-lkp@intel.com Acked-by: Vlastimil Babka Cc: Kent Overstreet Cc: Kees Cook Cc: Pasha Tatashin Signed-off-by: Andrew Morton --- include/linux/pgalloc_tag.h | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'include/linux/pgalloc_tag.h') diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h index 86ba5d33e43b..9cacadbd61f8 100644 --- a/include/linux/pgalloc_tag.h +++ b/include/linux/pgalloc_tag.h @@ -37,6 +37,9 @@ static inline union codetag_ref *get_page_tag_ref(struct page *page) static inline void put_page_tag_ref(union codetag_ref *ref) { + if (WARN_ON(!ref)) + return; + page_ext_put(page_ext_from_codetag_ref(ref)); } @@ -102,9 +105,11 @@ static inline struct alloc_tag *pgalloc_tag_get(struct page *page) union codetag_ref *ref = get_page_tag_ref(page); alloc_tag_sub_check(ref); - if (ref && ref->ct) - tag = ct_to_alloc_tag(ref->ct); - put_page_tag_ref(ref); + if (ref) { + if (ref->ct) + tag = ct_to_alloc_tag(ref->ct); + put_page_tag_ref(ref); + } } return tag; -- cgit v1.2.3 From fd8acc0097b91fab3104fa8a66ce2fd9cf8b0c11 Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Thu, 11 Jul 2024 15:04:56 -0700 Subject: lib: reuse page_ext_data() to obtain codetag_ref codetag_ref_from_page_ext() reimplements the same calculation as page_ext_data(). Reuse existing function instead. Link: https://lkml.kernel.org/r/20240711220457.1751071-2-surenb@google.com Fixes: dcfe378c81f7 ("lib: introduce support for page allocation tagging") Signed-off-by: Suren Baghdasaryan Cc: Kees Cook Cc: Kent Overstreet Cc: Pasha Tatashin Cc: Sourav Panda Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- include/linux/pgalloc_tag.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/pgalloc_tag.h') diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h index 9cacadbd61f8..acb1e9ce7981 100644 --- a/include/linux/pgalloc_tag.h +++ b/include/linux/pgalloc_tag.h @@ -15,7 +15,7 @@ extern struct page_ext_operations page_alloc_tagging_ops; static inline union codetag_ref *codetag_ref_from_page_ext(struct page_ext *page_ext) { - return (void *)page_ext + page_alloc_tagging_ops.offset; + return (union codetag_ref *)page_ext_data(page_ext, &page_alloc_tagging_ops); } static inline struct page_ext *page_ext_from_codetag_ref(union codetag_ref *ref) -- cgit v1.2.3 From 6ab42fe21c84d72da752923b4bd7075344f4a362 Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Thu, 11 Jul 2024 15:04:57 -0700 Subject: alloc_tag: fix page_ext_get/page_ext_put sequence during page splitting 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 Cc: Kees Cook Cc: Kent Overstreet Cc: Pasha Tatashin Cc: Sourav Panda Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- include/linux/pgalloc_tag.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'include/linux/pgalloc_tag.h') diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h index acb1e9ce7981..18cd0c0c73d9 100644 --- a/include/linux/pgalloc_tag.h +++ b/include/linux/pgalloc_tag.h @@ -71,6 +71,7 @@ static inline void pgalloc_tag_sub(struct page *page, unsigned int nr) 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(struct page *page, unsigned int nr) 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(struct page *page, unsigned int nr) 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) -- cgit v1.2.3