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Miller" , Dave Hansen , David Hildenbrand , Dmitry Vyukov , Ilias Apalodimas , Ingo Molnar , Jan Kara , Johannes Weiner , "Liam R. Howlett" , Lorenzo Stoakes , Madhavan Srinivasan , Marco Elver , Marek Szyprowski , Masami Hiramatsu , Michael Ellerman , Michal Hocko , Mike Rapoport , Nicholas Piggin , "H. Peter Anvin" , Rob Herring , Robin Murphy , Saravana Kannan , Suren Baghdasaryan , Thomas Gleixner , Vlastimil Babka , Will Deacon , Zi Yan , devicetree@vger.kernel.org, iommu@lists.linux.dev, kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org, linux-efi@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, x86@kernel.org Subject: [PATCH 8/8] memblock: warn when freeing reserved memory before memory map is initialized Date: Wed, 18 Mar 2026 12:58:27 +0200 Message-ID: <20260318105827.1358927-9-rppt@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260318105827.1358927-1-rppt@kernel.org> References: <20260318105827.1358927-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 7B3EF2000C X-Stat-Signature: ybg8ch713ayfyzffbtbrdjq71iuwfzsg X-Rspam-User: X-HE-Tag: 1773831613-649012 X-HE-Meta: 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 QbNOXPlw 9vh7s3RaeJw257Ht2mOVJi66cuKszgctAkKrZQcsCeJm4oeCj47VVVovF9OUcmwh7MRsoXOb6s+s1QjCWXbryC4vTmIlVAdJ7oBN6Nq5NTRoL+HLyBc7pcCs61W0oAGBiIKKD/MD5Maq+orFSvV0pUjDoezg5aeh0SC+PGkrsEzirrMx7MJGhxUyTvsWyXYGrro+cuyz8hHlq/ZXL//A/w1YANOWlWIWw8DaV70JS0brxQJEWJLHeNq9R8e5DqKpup4gM+2lrvpSUFS34AWK6F4aDbTbajmpzjVqP Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: "Mike Rapoport (Microsoft)" When CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, freeing of reserved memory before the memory map is fully initialized in deferred_init_memmap() would cause access to uninitialized struct pages and may crash when accessing spurious list pointers, like was recently discovered during discussion about memory leaks in x86 EFI code [1]. The trace below is from an attempt to call free_reserved_page() before page_alloc_init_late(): [ 0.076840] BUG: unable to handle page fault for address: ffffce1a005a0788 [ 0.078226] #PF: supervisor read access in kernel mode [ 0.078226] #PF: error_code(0x0000) - not-present page [ 0.078226] PGD 0 P4D 0 [ 0.078226] Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI [ 0.078226] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.12.68-92.123.amzn2023.x86_64 #1 [ 0.078226] Hardware name: Amazon EC2 t3a.nano/, BIOS 1.0 10/16/2017 [ 0.078226] RIP: 0010:__list_del_entry_valid_or_report+0x32/0xb0 ... [ 0.078226] __free_one_page+0x170/0x520 [ 0.078226] free_pcppages_bulk+0x151/0x1e0 [ 0.078226] free_unref_page_commit+0x263/0x320 [ 0.078226] free_unref_page+0x2c8/0x5b0 [ 0.078226] ? srso_return_thunk+0x5/0x5f [ 0.078226] free_reserved_page+0x1c/0x30 [ 0.078226] memblock_free_late+0x6c/0xc0 Currently there are not many callers of free_reserved_area() and they all appear to be at the right timings. Still, in order to protect against problematic code moves or additions of new callers add a warning that will inform that reserved pages cannot be freed until the memory map is fully initialized. [1] https://lore.kernel.org/all/e5d5a1105d90ee1e7fe7eafaed2ed03bbad0c46b.camel@kernel.crashing.org/ Signed-off-by: Mike Rapoport (Microsoft) --- mm/internal.h | 10 ++++++++++ mm/memblock.c | 5 +++++ mm/page_alloc.c | 10 ---------- 3 files changed, 15 insertions(+), 10 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index cb0af847d7d9..f60c1edb2e02 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1233,7 +1233,17 @@ static inline void vunmap_range_noflush(unsigned long start, unsigned long end) #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT DECLARE_STATIC_KEY_TRUE(deferred_pages); +static inline bool deferred_pages_enabled(void) +{ + return static_branch_unlikely(&deferred_pages); +} + bool __init deferred_grow_zone(struct zone *zone, unsigned int order); +#else +static inline bool deferred_pages_enabled(void) +{ + return false; +} #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */ void init_deferred_page(unsigned long pfn, int nid); diff --git a/mm/memblock.c b/mm/memblock.c index bd5758ff07f2..780e70d4971a 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -896,6 +896,11 @@ static unsigned long __free_reserved_area(phys_addr_t start, phys_addr_t end, { unsigned long pages = 0, pfn; + if (deferred_pages_enabled()) { + WARN(1, "Cannot free reserved memory because of deferred initialization of the memory map"); + return 0; + } + for_each_valid_pfn(pfn, PFN_UP(start), PFN_DOWN(end)) { struct page *page = pfn_to_page(pfn); void *direct_map_addr; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index df3d61253001..9ac47bab2ea7 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -331,11 +331,6 @@ int page_group_by_mobility_disabled __read_mostly; */ DEFINE_STATIC_KEY_TRUE(deferred_pages); -static inline bool deferred_pages_enabled(void) -{ - return static_branch_unlikely(&deferred_pages); -} - /* * deferred_grow_zone() is __init, but it is called from * get_page_from_freelist() during early boot until deferred_pages permanently @@ -348,11 +343,6 @@ _deferred_grow_zone(struct zone *zone, unsigned int order) return deferred_grow_zone(zone, order); } #else -static inline bool deferred_pages_enabled(void) -{ - return false; -} - static inline bool _deferred_grow_zone(struct zone *zone, unsigned int order) { return false; -- 2.51.0