From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 D95822C0268; Thu, 2 Jul 2026 02:03:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782957819; cv=none; b=GMzwwiVIJQO0UAyqcK8+nvXR7/NioYKccD2wnV2vaGIejULVfdP0+5O5nn192RolXnTYFwqOTRfoyFY17D/JxjLFlfBK5EZ9eObMA0FYXhKFjVqcLE3XV5BYA3j3gvJi3ggAOcQ3Fe+xBznnIMijg+2+GPaxCsTnbTo7SRqfgYw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782957819; c=relaxed/simple; bh=0E5/Qy4NS5/UKj3zIql3QL3cRmqjt0otCSTgfiSNF+A=; h=Date:To:From:Subject:Message-Id; b=qi5UfwpbRz+7YPGgFjGcOQ7jivDeScUMWjQ1iOkwwQgH41Ln6x1XFqVF7qX5bVKfbcPcfbVCb7bg4KQ5fE1tQwLxCKnrRgtYoXqd6voHQvj4ZOkcY80k54aNC/JHHynujCryJqSYonOefP7dQMokTqQHspHDVpXDKbYBM7ON+Ks= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=nbKPJViw; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="nbKPJViw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A4451F00A3A; Thu, 2 Jul 2026 02:03:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1782957817; bh=A1nMR+lL5N39L7ZXZcjAeXV60HSJwat3K5dE6Jcb2BI=; h=Date:To:From:Subject; b=nbKPJViw2xJDgjWtBEufphtrNV+CyGV63gPgqWxu4psho/ivK837j/xRNXznygoTV xMDN1XM9E5eauAL/Gz6TsVT7AAIBCmyRd8KwcrEbWhnauTMC12o/JheNc1pJaJ98xI KRxTTX2C+eeokwLlE8o1SLoBmTtdLLzzET3LCkPU= Date: Wed, 01 Jul 2026 19:03:37 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,willy@infradead.org,vbabka@kernel.org,surenb@google.com,stable@vger.kernel.org,rppt@kernel.org,mhocko@suse.com,luizcap@redhat.com,ljs@kernel.org,liam@infradead.org,jackmanb@google.com,hannes@cmpxchg.org,david@redhat.com,david@kernel.org,ketan.kishore@oss.qualcomm.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] mm-page_ext-add-count-limit-to-page_ext_iter_next-to-prevent-invalid-pfn-access.patch removed from -mm tree Message-Id: <20260702020337.6A4451F00A3A@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm: page_ext: add count limit to page_ext_iter_next to prevent invalid PFN access has been removed from the -mm tree. Its filename was mm-page_ext-add-count-limit-to-page_ext_iter_next-to-prevent-invalid-pfn-access.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Ketan Subject: mm: page_ext: add count limit to page_ext_iter_next to prevent invalid PFN access Date: Tue, 23 Jun 2026 02:48:04 +0530 The page_ext iteration API does not validate if the PFN still belongs to a valid section while advancing the iterator. When dynamically adding memory in the hotplug path, it can lead to a NULL pointer dereference during page_ext_lookup at the boundary of the last valid section when iterator count equals __pgcount. The for_each_page_ext() macro calls page_ext_iter_next() as its loop increment. for_each_page_ext() does a "__page_ext = page_ext_iter_next(&__iter)" at the end. This causes page_ext_iter_next() to increment iter->index past __pgcount and call page_ext_lookup(start_pfn + __pgcount). During memory hotplug (online), the PFN at start_pfn + __pgcount may belong to a section that has not yet been initialized, causing page_ext_lookup() to trigger a NULL pointer dereference. [ 14.555124][ T846] Call trace: [ 14.555125][ T846] lookup_page_ext+0x6c/0x108 (P) [ 14.555127][ T846] page_ext_lookup+0x30/0x3c [ 14.555129][ T846] __reset_page_owner+0x11c/0x260 [ 14.571201][ T846] __free_pages_ok+0x5e8/0x8e0 [ 14.571204][ T846] __free_pages_core+0x78/0xf0 [ 14.571206][ T846] generic_online_page+0x14/0x24 [ 14.597782][ T846] online_pages+0x178/0x30c [ 14.597784][ T846] memory_block_change_state+0x284/0x32c [ 14.597787][ T846] memory_subsys_online+0x4c/0x64 [ 14.597789][ T846] device_online+0x88/0xb0 [ 14.597791][ T846] online_memory_block+0x30/0x40 [ 14.597793][ T846] walk_memory_blocks+0xac/0xe8 [ 14.597794][ T846] add_memory_resource+0x280/0x298 [ 14.656161][ T846] add_memory+0x60/0x98 Move the iteration boundary enforcement inside the iterator functions, so callers cannot inadvertently access beyond the requested range. Link: https://lore.kernel.org/20260623-page_ext-v3-1-a89799a5367c@oss.qualcomm.com Fixes: 9039b9096ea2 ("mm: page_ext: add an iteration API for page extensions") Signed-off-by: Ketan Kishore Suggested-by: David Hildenbrand Suggested-by: Matthew Wilcox Acked-by: Zi Yan Acked-by: David Hildenbrand (Arm) Cc: Brendan Jackman Cc: Johannes Weiner Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Luiz Capitulino Cc: Michal Hocko Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton --- include/linux/page_ext.h | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) --- a/include/linux/page_ext.h~mm-page_ext-add-count-limit-to-page_ext_iter_next-to-prevent-invalid-pfn-access +++ a/include/linux/page_ext.h @@ -120,14 +120,18 @@ struct page_ext_iter { * page_ext_iter_begin() - Prepare for iterating through page extensions. * @iter: page extension iterator. * @pfn: PFN of the page we're interested in. + * @count: maximum number of page extensions to return. * * Must be called with RCU read lock taken. * * Return: NULL if no page_ext exists for this page. */ static inline struct page_ext *page_ext_iter_begin(struct page_ext_iter *iter, - unsigned long pfn) + unsigned long pfn, unsigned long count) { + if (!count) + return NULL; + iter->index = 0; iter->start_pfn = pfn; iter->page_ext = page_ext_lookup(pfn); @@ -138,19 +142,22 @@ static inline struct page_ext *page_ext_ /** * page_ext_iter_next() - Get next page extension * @iter: page extension iterator. + * @count: maximum number of page extensions to return. * * Must be called with RCU read lock taken. * * Return: NULL if no next page_ext exists. */ -static inline struct page_ext *page_ext_iter_next(struct page_ext_iter *iter) +static inline struct page_ext *page_ext_iter_next(struct page_ext_iter *iter, + unsigned long count) { unsigned long pfn; if (WARN_ON_ONCE(!iter->page_ext)) return NULL; - iter->index++; + if (++iter->index >= count) + return NULL; pfn = iter->start_pfn + iter->index; if (page_ext_iter_next_fast_possible(pfn)) @@ -183,9 +190,9 @@ static inline struct page_ext *page_ext_ * IMPORTANT: must be called with RCU read lock taken. */ #define for_each_page_ext(__page, __pgcount, __page_ext, __iter) \ - for (__page_ext = page_ext_iter_begin(&__iter, page_to_pfn(__page));\ - __page_ext && __iter.index < __pgcount; \ - __page_ext = page_ext_iter_next(&__iter)) + for (__page_ext = page_ext_iter_begin(&__iter, page_to_pfn(__page), __pgcount); \ + __page_ext; \ + __page_ext = page_ext_iter_next(&__iter, __pgcount)) #else /* !CONFIG_PAGE_EXTENSION */ struct page_ext; _ Patches currently in -mm which might be from ketan.kishore@oss.qualcomm.com are