From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0a-0031df01.pphosted.com (mx0a-0031df01.pphosted.com [205.220.168.131]) (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 185543AA1A9 for ; Mon, 22 Jun 2026 14:15:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=205.220.168.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782137706; cv=none; b=uwF5wmhX7FiS+wYdS9+NHZoie8A3vG+VxgNZPuClA0tlU6L1z9iaUDMegWH5NJ8+iD+lytZTiylwTEx7jJMGHnaZwNcv5nxjjLmB1ntMMn+/tVQrwftLxLNmSkDrcQ0gTdauqzCnvyQDrFohb6aVL8hxkFXx6068ykYkJeiWvtk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782137706; c=relaxed/simple; bh=NNyPibn7P54f63BQb5tNU5XeaeS5Q9Dj4omuy0PXFws=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=uYn2N1Qa7wulHyH36Dehweot9v2S2XFV0kz6WZ9zRltFxQ++KrXF0SB10bTXsr+jJ5Y1MLvNLjG8xPZgPk1+g5dx07YRLnTTJ63X6iAJ8/93LSldL6SFMNhxlCKBbo4J8mxsglYEYRgRsnx6ap72l6yaeruM1aDDx4i4LQAFfDA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oss.qualcomm.com; spf=pass smtp.mailfrom=oss.qualcomm.com; dkim=pass (2048-bit key) header.d=qualcomm.com header.i=@qualcomm.com header.b=Rh7s5zWv; dkim=pass (2048-bit key) header.d=oss.qualcomm.com header.i=@oss.qualcomm.com header.b=PlfYuptC; arc=none smtp.client-ip=205.220.168.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oss.qualcomm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=oss.qualcomm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=qualcomm.com header.i=@qualcomm.com header.b="Rh7s5zWv"; dkim=pass (2048-bit key) header.d=oss.qualcomm.com header.i=@oss.qualcomm.com header.b="PlfYuptC" Received: from pps.filterd (m0279863.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 65MDG9Og2387009 for ; Mon, 22 Jun 2026 14:15:04 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=qualcomm.com; h= cc:content-transfer-encoding:content-type:date:from:message-id :mime-version:subject:to; s=qcppdkim1; bh=piffdiB759PLk/akI9k0fY EicyM6im7+yWgCdw1Qj5g=; b=Rh7s5zWvgufeNB3bcG4uRUdrek+rbJfP4Oku2k p1xL/ot+CjmuaNijQvcxpY5baDYBLbwfomN0QvggpinaCcPWfPQ+vclc8qW3thrv DwBbFvFk+Zbhs2xc53qmnLZ0sLJiQfd2+fERbv/J77pbqU4wqFqf5cChyPCWVvI7 ys8P+q8YLWlyaJQXe1HF6V3hMArJvNGE84Wx09+Djs9rqNhmzeiZY1c53rJztMnQ iPSVPphpF97fa/BLe+yuZM/nAP08hQSjHuPUPPmm3JuRftHchK4so1R8EQbcRrJE kBcfPgLPdIAXOWXCKCj2Ur571JydRPqBGEBMm3gVs0tvwpjw== Received: from mail-pj1-f70.google.com (mail-pj1-f70.google.com [209.85.216.70]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 4ey5sn06ue-1 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NOT) for ; Mon, 22 Jun 2026 14:15:04 +0000 (GMT) Received: by mail-pj1-f70.google.com with SMTP id 98e67ed59e1d1-37ca93a9253so2941351a91.1 for ; Mon, 22 Jun 2026 07:15:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oss.qualcomm.com; s=google; t=1782137704; x=1782742504; darn=vger.kernel.org; h=cc:to:message-id:content-transfer-encoding:mime-version:subject :date:from:from:to:cc:subject:date:message-id:reply-to; bh=piffdiB759PLk/akI9k0fYEicyM6im7+yWgCdw1Qj5g=; b=PlfYuptC2Z1edQ0Nk+kdbAgNGJF3PXbtxMv3klSUxIR7gOO/uEb57P3uz9KwbBERXG LqxMxEKRkrE6kyXkgFu6VIr3FGE713ZB4/7lIk06uriqbYH8Tk0SsQsTgddvCt8lZlUz Brjx9O2ubcj5+2rfM2VYQjKdVHPQ6T6T7SgG/5OOmhpp5u84gRbKjalmdIFvOc4uN9Cb Vo3iStlMX9748BpETozdDSfYZvxfNYbmPX2+p+MWzBGlsbtuOLDxaLunLfUpVaMDjTmW DMA4832Jg9RtUlGuvr7dlDZiq+zsYB+QL5bEzOmFgAGumRvNDRZ8rm8ycKzoPwmJqouH ggwg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782137704; x=1782742504; h=cc:to:message-id:content-transfer-encoding:mime-version:subject :date:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=piffdiB759PLk/akI9k0fYEicyM6im7+yWgCdw1Qj5g=; b=o9RmeBdgN1e/ej2kmbCxICdXoqCL9uytC4Z58T3FEgtgqNUD4157CeoHbqjPNSE8D7 a+MkeQuDo6A+NHNOKHx7SipPP4e6pZ9UD1tDAbzYxm1Hj6ETWT5FXs4Nky2fjJRcsc2T uiWUpEJk6BjGsqP2890GPR0adm3XPPadMZnM7U30ido/+Ycgicrnuihs6vrO6W8dGkcm b35jX2A/QecuAJalNrXpP36/S/eX7JohiZtlbWiRtq3uIZtszt9drCPZ00k4+tb8vhp3 ec+19AiWcBQ3CzEBhUzbSEL85CcAo7vO/uK9umg7/dd/9+LMa5q8Muvzvm6/g5hqwGWS zZFg== X-Forwarded-Encrypted: i=1; AHgh+Rp4lOD5yf6c+BPl+NLC6O0KigxfRdFnuFYl6IadajpQRoEvHsGriX9J+OoJuF/Y974nKz6dcJp6OByC70U=@vger.kernel.org X-Gm-Message-State: AOJu0Yy65Az+3M/utxbN07oKBIsglzm+nL2uvCpB3f+6odMGKSQsYm9o LwJGH41SOK+Ts8M4livUZzELsLgguD5WGuBiEb+sKAKk1zGyDVCHgo4jKq9gG+c2ExzDUesnCYv NZLAaOdZBiqmjAbNDFpX3Yob+c+9T965WAWS1mGIIRehSBWaHOzYXzwfL2uYW6Rt2gpfP+8Qo+Z A= X-Gm-Gg: AfdE7cmBawfXa3hRN2neQw0go8oibedHuwipmo+Qlm1u5YZw4R6+x9Y17i/JqQIp+PQ cImU+UQLXjq+zWEXbzwXf6rHyJ+s/a5fnVkzzvrJzcUAgarATwq6ej7Kl0QmjxzwZjEi5MRI2Va jDDiWhzl/eW8mRnv5SSf3zk2sfvzDMkQI8W/YUf35W2/F2B6HcJlnFVh7uj4aB8NTS+G/VU0Haq L9iqynfr9T1UprxP8YFChua8MTTIQJrQjjDpidY8lpJp0cTuAmrrHKg9+9YaHCHCpI/0dWyD6ct EN65yJlTpvDHTp+p/r25ZGfANM5z2YPwbb+hIkLxer9BVQhf54Sp717xpKSyAIyoDcNYVhNvRDb G8s7UD8AYTfJGkoJd8d1tkC8aEnaIqQ5CnWPaG6oMq33o X-Received: by 2002:a17:90b:4a05:b0:369:a359:b181 with SMTP id 98e67ed59e1d1-37d4e86bf8amr11351191a91.23.1782137703343; Mon, 22 Jun 2026 07:15:03 -0700 (PDT) X-Received: by 2002:a17:90b:4a05:b0:369:a359:b181 with SMTP id 98e67ed59e1d1-37d4e86bf8amr11351115a91.23.1782137702690; Mon, 22 Jun 2026 07:15:02 -0700 (PDT) Received: from hu-ketakish-hyd.qualcomm.com ([202.46.22.19]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-37d1558b599sm10382253a91.7.2026.06.22.07.14.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jun 2026 07:15:02 -0700 (PDT) From: Ketan Date: Mon, 22 Jun 2026 19:44:54 +0530 Subject: [PATCH v2] mm: page_ext: add count limit to page_ext_iter_next to prevent invalid PFN access Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260622-page_ext-v2-1-135d4cfbc42f@oss.qualcomm.com> X-B4-Tracking: v=1; b=H4sIAF1DOWoC/0WNQQqDMBBFryKzbsTEJkpXvUeREuOoKdXYjIpFv HujpXQz8OD9NysQeosEl2gFj7Ml6/oA4hSBaXXfILNVYBCJUIniig26wTsuI0s51lLKs1S1gaA PHmu7HKlb8WWaygeacd/vRmtpdP59/Jr57v2y2T87c8ZZmukqT0TJdZpfHVH8mvTTuK6Lw4Fi2 7YPXaj/8rkAAAA= X-Change-ID: 20260616-page_ext-31ef555456fc To: Andrew Morton , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Luiz Capitulino , David Hildenbrand Cc: kernel@oss.qualcomm.com, stable@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Matthew Wilcox , Ketan Kishore , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , David Hildenbrand X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1782137697; l=5361; i=ketan.kishore@oss.qualcomm.com; s=20260617; h=from:subject:message-id; bh=NNyPibn7P54f63BQb5tNU5XeaeS5Q9Dj4omuy0PXFws=; b=x3ahtd2rZYMUyig22NRD3pdqrNVhc/v5mZUHL3Dqupr++LwdYEppRZ4I9G4BQiccDsqOLvMEa UuRC8mI5d6mDeEqG3F1Y87zdS+UczTa95RQVa/JXI0h+AWiUbPPiT1T X-Developer-Key: i=ketan.kishore@oss.qualcomm.com; a=ed25519; pk=4sb5Ima5x03wc0KSnl57v8kR/7FxMt01+xlZJ53rSJU= X-Proofpoint-GUID: fwbzLME7mDnaLHobINVJYdPyPIC59Kws X-Proofpoint-ORIG-GUID: fwbzLME7mDnaLHobINVJYdPyPIC59Kws X-Authority-Analysis: v=2.4 cv=PuKjqQM3 c=1 sm=1 tr=0 ts=6a394368 cx=c_pps a=0uOsjrqzRL749jD1oC5vDA==:117 a=fChuTYTh2wq5r3m49p7fHw==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yOCtJkima9RkubShWh1s:22 a=bC-a23v3AAAA:8 a=EUspDBNiAAAA:8 a=VwQbUJbxAAAA:8 a=20KFwNOVAAAA:8 a=JfrnYn6hAAAA:8 a=Z4Rwk6OoAAAA:8 a=1XWaLZrsAAAA:8 a=iox4zFpeAAAA:8 a=37rDS-QxAAAA:8 a=v2oVMEoAPVEBj90iUNMA:9 a=QEXdDO2ut3YA:10 a=mQ_c8vxmzFEMiUWkPHU9:22 a=FO4_E8m0qiDe52t0p3_H:22 a=1CNFftbPRP8L7MoqJWF3:22 a=HkZW87K1Qel5hWWM3VKY:22 a=WzC6qhA0u3u7Ye7llzcV:22 a=k1Nq6YrhK2t884LQW06G:22 X-Proofpoint-Spam-Info: AW1haW4tMjYwNjIyMDE0MSBTYWx0ZWRfX78Bav20zl5KJ w1snLCI7jioX0Hs8wc27jsk+esEc45Pm9cBVxi50Aq/vGlgXts19WJLmqnNqbMq0zF8X5jL4Y2R w7GCu2f7zyLHpuwBoyx/8Qfiw/Sfc7o= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjIyMDE0MSBTYWx0ZWRfX1kMix/nAg3e4 WbYD9uzU0H060+qOjFo4xl5g2MVfHOGckfIHYC21rYwDa5hUa2Vv/DbQ6+jz5u+6/GSfhGGPkGi +yhZjQY8cUsEo5l2D3I4Aa5YDp3w5pojGd2ssDPzA2aRPLE9hdsKmbYAqs7k0ImotE6L9yoEYIr jR+x4ewrO7A5x5rlGLptDVV1hWVMDCmZjy4JwFdA0CcxNWjQdvd8sk1h/D3bywHeYpYJDauVi66 +L0Vv+pah7EKFGSkLIhyOkNOlcUFzv3oTVv1TGzYe7afiRKTd40LidLNn9zoG8+3PvXT1hZJIpd MbrdnZYOqDcXE10i73BpnpKn6CYDyO/ZCHKudfL4dVd+6lto/zJlAFZOozMA7QbnBCIuQKN8jui 5sBNAuTXKZ4gkmMYFoEbiDHlcwU+19iTA6rMCCWPaFo9faXuBKmOFo8ReFN3blnpK7TEoDnhdxi lP6UMfPC5cVf8Ar78JQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-22_02,2026-06-22_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=0 priorityscore=1501 phishscore=0 impostorscore=0 adultscore=0 clxscore=1015 bulkscore=0 spamscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606220141 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. Fixes: 9039b9096ea2 ("mm: page_owner: use new iteration API") Cc: stable@vger.kernel.org Suggested-by: David Hildenbrand Suggested-by: Matthew Wilcox Signed-off-by: Ketan Kishore --- Changes in v2: - Incorporated comments from David and Matthew to check for invalid PFN in page_ext iterator rather than checking for NULL section in page_ext_lookup. - Minor improvement in commit description to include the issue with page_ext_iter_next - Link to v1: https://patch.msgid.link/20260617-page_ext-v1-1-37ad802b1a38@oss.qualcomm.com To: Andrew Morton To: David Hildenbrand To: Lorenzo Stoakes To: "Liam R. Howlett" To: Vlastimil Babka To: Mike Rapoport To: Suren Baghdasaryan To: Michal Hocko To: Luiz Capitulino Cc: kernel@oss.qualcomm.com Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org --- include/linux/page_ext.h | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h index 61e876e255e8..4f7d7a8709de 100644 --- a/include/linux/page_ext.h +++ b/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 == 0) + 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_iter_begin(struct page_ext_iter *iter, /** * 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_iter_get(const struct page_ext_iter *ite * 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; --- base-commit: c425609d6ac4012c8bbf01ec2e10e801b1923a7b change-id: 20260616-page_ext-31ef555456fc Best regards, -- Ketan Kishore