From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-186.mta0.migadu.com (out-186.mta0.migadu.com [91.218.175.186]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EAE0D28DC4 for ; Tue, 30 Jun 2026 06:32:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.186 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782801160; cv=none; b=N+ZkxJM6vwR8KKO87VbBFRLe4JL2VEvZHexqg5jbquGA6ijMm19wCY7ZKWFhtVYpjOJjF855mwQrFu3Ryd+ATpn5WYDIgjRAxJkMUiCGq2ej9Y6uGXa/pxbtLn3mZWfu7b34AGMlDPFsasQzXiBWvttBpv5Wc3+9wRww1C3SuwI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782801160; c=relaxed/simple; bh=z3Bv3tMgQV0fvaNV0h8o292zl9B8JyHfa6x6vU9SUHY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=rPGP+D/DdMll6DOIKHCkqOgrXMhuAhE82pAjlpQvG2hnuPUiqKTXwZDTvQ9V6as6BeOayyAFSfCruxti09+tFw6Y2c5o0K/+pC4V4Fp6v8YHMAUCYnC883pTYpJ8LUbV22dg8p1YThprPMUeXYIlyEe9v/RRRafhm+3PqFAAZcY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=Td1Lrh6w; arc=none smtp.client-ip=91.218.175.186 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="Td1Lrh6w" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782801155; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=KjNfxEY8O5b1YS1IpfKgKUs7d5wF9xctyGq1gJiAwLQ=; b=Td1Lrh6wryQOdq8Zhf9sDe/8DLzzlATuFn8LitsFOvSOkMiYjqGX5bJouNE/PXZ5h1fM6r 5YkpDUClM+HBTtFX8Dc188LD+yPIwWycVP+2hQNsR05nVyRYcsKxVKnzdlr9Sd6ErzziEQ W/Y3ftiUTVSwaehM7yxoUsVxZKliSuU= From: Hui Zhu To: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Hui Zhu Subject: [PATCH v8] mm: fix ASSERT_EXCLUSIVE_BITS by passing memdesc_flags_t by pointer Date: Tue, 30 Jun 2026 14:32:16 +0800 Message-ID: <20260630063216.417897-1-hui.zhu@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Hui Zhu KCSAN reports a data race between page_to_nid()/folio_pgdat() reading page->flags and folio_trylock()/folio_lock() concurrently doing test_and_set_bit_lock(PG_locked, ...) on the same word, e.g.: BUG: KCSAN: data-race in __lruvec_stat_mod_folio / shmem_get_folio_gfp The race is benign: nid/zone bits are set once at page init and never overlap with PG_locked. However, ASSERT_EXCLUSIVE_BITS() inside memdesc_nid/zonenum() was checking a by-value copy of the flags word, not the live page->flags, so it failed to annotate the real access. Change memdesc_nid(), memdesc_zonenum(), memdesc_section(), and memdesc_is_zone_device() to take a const memdesc_flags_t * and update all callers to pass &page->flags / &folio->flags, so ASSERT_EXCLUSIVE_BITS() operates on the actual shared word. Guard the ASSERT_EXCLUSIVE_BITS() calls in memdesc_zonenum() and memdesc_section() under ZONES_WIDTH != 0 / SECTIONS_WIDTH != 0 to avoid a zero-mask check on configs where the corresponding field is absent. Under CONFIG_NUMA=n, stub out page_to_nid() and folio_nid() as plain "return 0" instead of reading page->flags when NODES_MASK is 0 and the check can never fire. Signed-off-by: Hui Zhu Co-developed-by: David Hildenbrand (Arm) Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Hui Zhu --- Changelog: v8: According to the comments of Andrew, include kcsan-checks.h in mm.h. Incorporate David's patch that switch memdesc_nid(), memdesc_zonenum(), memdesc_section() and memdesc_is_zone_device() to take a const memdesc_flags_t * instead of using a per-accessor macro/call-site hack. Update all callers accordingly and extend the same exclusive-bits check to memdesc_section() and memdesc_is_zone_device(), guarded by SECTIONS_WIDTH != 0 / reusing ZONES_WIDTH != 0 to avoid zero-mask checks on configs without the corresponding field. v7: According to the comments of Sashiko, restrict the memdesc_nid() macro to CONFIG_NUMA, keeping a plain "return 0" static inline stub otherwise, and re-add a local page pointer in page_to_nid() to avoid evaluating PF_POISONED_CHECK(page) twice. v6: According to the comments of David, turn memdesc_nid() from a static inline function into a macro so ASSERT_EXCLUSIVE_BITS() can check the caller's page->flags/folio->flags directly. v5: According to the comments of Sashiko, guard the ASSERT_EXCLUSIVE_BITS() calls with #ifndef NODE_NOT_IN_PAGE_FLAGS (for nid) and #if ZONES_WIDTH != 0 (for zonenum). According to the comments of David, avoid calling PF_POISONED_CHECK(page) twice in page_to_nid(). According to the warning of lkp, switch the CONFIG_NUMA=n page_to_nid()/folio_nid() stubs from macros to static inline functions. v4: According to the comments of Andrew and Sashiko, set page_to_nid()/folio_nid() as static inline stubs returning 0 under CONFIG_NUMA=n. v3: According to the comments of Andrew and Sashiko, move ASSERT_EXCLUSIVE_BITS out of memdesc_nid()/memdesc_zonenum() into the page/folio call sites. v2: According to the comments of David, remove useless comments and use ASSERT_EXCLUSIVE_BITS() in memdesc_nid() instead of data_race() in page_to_nid(). include/asm-generic/memory_model.h | 2 +- include/linux/mm.h | 40 ++++++++++++++++++++++++------ include/linux/mm_inline.h | 4 +-- include/linux/mmzone.h | 26 ++++++++++--------- mm/page_alloc.c | 6 ++--- mm/slab.h | 2 +- mm/sparse.c | 2 +- 7 files changed, 54 insertions(+), 28 deletions(-) diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h index efa6610acbc7..f8404bc7773c 100644 --- a/include/asm-generic/memory_model.h +++ b/include/asm-generic/memory_model.h @@ -53,7 +53,7 @@ static inline int pfn_valid(unsigned long pfn) */ #define __page_to_pfn(pg) \ ({ const struct page *__pg = (pg); \ - int __sec = memdesc_section(__pg->flags); \ + int __sec = memdesc_section(&__pg->flags); \ (unsigned long)(__pg - __section_mem_map_addr(__nr_to_section(__sec))); \ }) diff --git a/include/linux/mm.h b/include/linux/mm.h index 485df9c2dbdd..315d8917f8e7 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -37,6 +37,7 @@ #include #include #include +#include struct mempolicy; struct anon_vma; @@ -2286,23 +2287,45 @@ static inline int page_zone_id(struct page *page) } #ifdef NODE_NOT_IN_PAGE_FLAGS -int memdesc_nid(memdesc_flags_t mdf); +int memdesc_nid(const memdesc_flags_t *mdf); #else -static inline int memdesc_nid(memdesc_flags_t mdf) +#ifdef CONFIG_NUMA +static inline int memdesc_nid(const memdesc_flags_t *mdf) { - return (mdf.f >> NODES_PGSHIFT) & NODES_MASK; + ASSERT_EXCLUSIVE_BITS(mdf->f, NODES_MASK << NODES_PGSHIFT); + return (mdf->f >> NODES_PGSHIFT) & NODES_MASK; +} +#else +static inline int memdesc_nid(const memdesc_flags_t *mdf) +{ + return 0; } #endif +#endif +#ifdef CONFIG_NUMA static inline int page_to_nid(const struct page *page) { - return memdesc_nid(PF_POISONED_CHECK(page)->flags); + const struct page *p = PF_POISONED_CHECK(page); + + return memdesc_nid(&p->flags); } static inline int folio_nid(const struct folio *folio) { - return memdesc_nid(folio->flags); + return memdesc_nid(&folio->flags); } +#else +static inline int page_to_nid(const struct page *page) +{ + return 0; +} + +static inline int folio_nid(const struct folio *folio) +{ + return 0; +} +#endif #ifdef CONFIG_NUMA_BALANCING /* page access time bits needs to hold at least 4 seconds */ @@ -2541,12 +2564,13 @@ static inline void set_page_section(struct page *page, unsigned long section) page->flags.f |= (section & SECTIONS_MASK) << SECTIONS_PGSHIFT; } -static inline unsigned long memdesc_section(memdesc_flags_t mdf) +static inline unsigned long memdesc_section(const memdesc_flags_t *mdf) { - return (mdf.f >> SECTIONS_PGSHIFT) & SECTIONS_MASK; + ASSERT_EXCLUSIVE_BITS(mdf->f, SECTIONS_MASK << SECTIONS_PGSHIFT); + return (mdf->f >> SECTIONS_PGSHIFT) & SECTIONS_MASK; } #else /* !SECTION_IN_PAGE_FLAGS */ -static inline unsigned long memdesc_section(memdesc_flags_t mdf) +static inline unsigned long memdesc_section(const memdesc_flags_t *mdf) { return 0; } diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index a8430a7ae054..efcddb9925ad 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -650,7 +650,7 @@ static inline bool vma_has_recency(const struct vm_area_struct *vma) static inline size_t num_pages_contiguous(struct page **pages, size_t nr_pages) { struct page *cur_page = pages[0]; - unsigned long section = memdesc_section(cur_page->flags); + unsigned long section = memdesc_section(&cur_page->flags); size_t i; for (i = 1; i < nr_pages; i++) { @@ -660,7 +660,7 @@ static inline size_t num_pages_contiguous(struct page **pages, size_t nr_pages) * In unproblematic kernel configs, page_to_section() == 0 and * the whole check will get optimized out. */ - if (memdesc_section(cur_page->flags) != section) + if (memdesc_section(&cur_page->flags) != section) break; } diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index ca2712187147..e60dad546ca6 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1272,31 +1272,33 @@ static inline bool zone_is_empty(const struct zone *zone) #define KASAN_TAG_MASK ((1UL << KASAN_TAG_WIDTH) - 1) #define ZONEID_MASK ((1UL << ZONEID_SHIFT) - 1) -static inline enum zone_type memdesc_zonenum(memdesc_flags_t flags) +static inline enum zone_type memdesc_zonenum(const memdesc_flags_t *flags) { - ASSERT_EXCLUSIVE_BITS(flags.f, ZONES_MASK << ZONES_PGSHIFT); - return (flags.f >> ZONES_PGSHIFT) & ZONES_MASK; +#if ZONES_WIDTH != 0 + ASSERT_EXCLUSIVE_BITS(flags->f, ZONES_MASK << ZONES_PGSHIFT); +#endif + return (flags->f >> ZONES_PGSHIFT) & ZONES_MASK; } static inline enum zone_type page_zonenum(const struct page *page) { - return memdesc_zonenum(page->flags); + return memdesc_zonenum(&page->flags); } static inline enum zone_type folio_zonenum(const struct folio *folio) { - return memdesc_zonenum(folio->flags); + return memdesc_zonenum(&folio->flags); } #ifdef CONFIG_ZONE_DEVICE -static inline bool memdesc_is_zone_device(memdesc_flags_t mdf) +static inline bool memdesc_is_zone_device(const memdesc_flags_t *mdf) { return memdesc_zonenum(mdf) == ZONE_DEVICE; } static inline struct dev_pagemap *page_pgmap(const struct page *page) { - VM_WARN_ON_ONCE_PAGE(!memdesc_is_zone_device(page->flags), page); + VM_WARN_ON_ONCE_PAGE(!memdesc_is_zone_device(&page->flags), page); return page_folio(page)->pgmap; } @@ -1311,9 +1313,9 @@ static inline struct dev_pagemap *page_pgmap(const struct page *page) static inline bool zone_device_pages_have_same_pgmap(const struct page *a, const struct page *b) { - if (memdesc_is_zone_device(a->flags) != memdesc_is_zone_device(b->flags)) + if (memdesc_is_zone_device(&a->flags) != memdesc_is_zone_device(&b->flags)) return false; - if (!memdesc_is_zone_device(a->flags)) + if (!memdesc_is_zone_device(&a->flags)) return true; return page_pgmap(a) == page_pgmap(b); } @@ -1321,7 +1323,7 @@ static inline bool zone_device_pages_have_same_pgmap(const struct page *a, extern void memmap_init_zone_device(struct zone *, unsigned long, unsigned long, struct dev_pagemap *); #else -static inline bool memdesc_is_zone_device(memdesc_flags_t mdf) +static inline bool memdesc_is_zone_device(const memdesc_flags_t *mdf) { return false; } @@ -1338,12 +1340,12 @@ static inline struct dev_pagemap *page_pgmap(const struct page *page) static inline bool is_zone_device_page(const struct page *page) { - return memdesc_is_zone_device(page->flags); + return memdesc_is_zone_device(&page->flags); } static inline bool folio_is_zone_device(const struct folio *folio) { - return memdesc_is_zone_device(folio->flags); + return memdesc_is_zone_device(&folio->flags); } static inline bool is_zone_movable_page(const struct page *page) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ee902a468c2f..020a97ca018e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6904,15 +6904,15 @@ static void __free_contig_range_common(unsigned long pfn, unsigned long nr_pages continue; } - if (start && memdesc_section(page->flags) != start_sec) { + if (start && memdesc_section(&page->flags) != start_sec) { free_prepared_contig_range(start, i - nr_start); start = page; nr_start = i; - start_sec = memdesc_section(page->flags); + start_sec = memdesc_section(&page->flags); } else if (!start) { start = page; nr_start = i; - start_sec = memdesc_section(page->flags); + start_sec = memdesc_section(&page->flags); } } diff --git a/mm/slab.h b/mm/slab.h index 281a65233795..9ded319495a0 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -179,7 +179,7 @@ static inline void *slab_address(const struct slab *slab) static inline int slab_nid(const struct slab *slab) { - return memdesc_nid(slab->flags); + return memdesc_nid(&slab->flags); } static inline pg_data_t *slab_pgdat(const struct slab *slab) diff --git a/mm/sparse.c b/mm/sparse.c index 16ac6df3c89f..8e3847764513 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -43,7 +43,7 @@ static u8 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned; static u16 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned; #endif -int memdesc_nid(memdesc_flags_t mdf) +int memdesc_nid(const memdesc_flags_t *mdf) { return section_to_node_table[memdesc_section(mdf)]; } -- 2.43.0