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 3C93B41D4F1; Fri, 7 Aug 2026 14:47:15 +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=1786114038; cv=none; b=B7btTTkYZ/dx+J4SeGwA5AYA98xsbRpK9iob9DxxfgIpqAUnW9z0c/b9ZxesUkx5NGw8o7gJMqbCzllWKXBREWSeSoWO167xXgJCzRXHwrAH7clDQWG8szlx8Itv2VDSRzr88Fz8NVeA9WqYzCRP1Y/4U/jBigY6Ic/fb7SQId0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786114038; c=relaxed/simple; bh=hLajU9ahbV22UdQWzAOgqX8a5YZWLKcsTSMkRJtNiEs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=u0pC6VkPk5L/4MmtlTJdlwZDb4dLUBnmdMXGmoIACh/H0FB1upkdkB0dH5Kvuj8On6W3Uapg1MsvaJTKmU04p2WgNsJPCqIE8oaLhGFrHA6InTx7FqRVrxYFqkE70UnJtZGKEo6JhqTfhNyEFQ68jCtYOPNSjXXKNEs/oRxhekQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xgmX3CIS; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="xgmX3CIS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8E111F000E9; Fri, 7 Aug 2026 14:47:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786114034; bh=SDvU6/U+/+7Dm8IRGTVUtMn8Jd4CxdejuBf9DS0QLIU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=xgmX3CISllZh3GYOonnoTAgoQgIoSGAFKCiwcIQRuJUkNDR9LlQzGUjEpsfeprZoD ml8RJoibVlYRyi8BrN62K69ZYTbWcVCPfvj8qd5GMklC6vMGkigtYMoQ46+0Hh0jst gveE/LwzAAR/aHgQuIkdYKGw60SB9DZ6CDPQpqdM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Karl Mehltretter , Paul Walmsley , Sasha Levin Subject: [PATCH 6.12 119/337] riscv: mm: Fix out-of-bounds page-table walk during memory hot-remove Date: Fri, 7 Aug 2026 16:35:22 +0200 Message-ID: <20260807143421.110176283@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260807143418.516897842@linuxfoundation.org> References: <20260807143418.516897842@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Karl Mehltretter [ Upstream commit a0188cc133696627857d16054e43f9ebc7efc821 ] remove_pud_mapping() and remove_p4d_mapping() obtain a child table base with pud_offset(p4dp, 0) and p4d_offset(pgd, 0), then add the index for addr. RISC-V folds page-table levels at runtime. When a level is folded, its offset helper returns the parent entry itself, but the index can still be nonzero. Adding it walks past the parent table. Sv48 folds P4D, while Sv39 folds both P4D and PUD, so memory hot-remove can descend into unrelated memory and pass an invalid page to __free_pages(). This can trigger: kernel BUG at include/linux/mm.h:1810! VM_BUG_ON_PAGE(page_ref_count(page) == 0) arch_remove_memory+0x1e/0x5c try_remove_memory+0x15e/0x200 remove_memory+0x24/0x3c Only add the index when the corresponding page-table level is enabled, matching p4d_offset() and pud_offset(). Fixes: c75a74f4ba19 ("riscv: mm: Add memory hotplugging support") Assisted-by: Claude:claude-fable-5 Signed-off-by: Karl Mehltretter Link: https://patch.msgid.link/20260729012132.24882-1-kmehltretter@gmail.com Signed-off-by: Paul Walmsley Signed-off-by: Sasha Levin --- arch/riscv/mm/init.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index 4594f77a06ee3..e52f7dabb370c 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -1726,7 +1726,7 @@ static void __meminit remove_pud_mapping(pud_t *pud_base, unsigned long addr, un for (; addr < end; addr = next) { next = pud_addr_end(addr, end); - pudp = pud_base + pud_index(addr); + pudp = pgtable_l4_enabled ? pud_base + pud_index(addr) : pud_base; pud = pudp_get(pudp); if (!pud_present(pud)) continue; @@ -1757,7 +1757,7 @@ static void __meminit remove_p4d_mapping(p4d_t *p4d_base, unsigned long addr, un for (; addr < end; addr = next) { next = p4d_addr_end(addr, end); - p4dp = p4d_base + p4d_index(addr); + p4dp = pgtable_l5_enabled ? p4d_base + p4d_index(addr) : p4d_base; p4d = p4dp_get(p4dp); if (!p4d_present(p4d)) continue; -- 2.53.0