From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794453995; b=papVpmkXzZEzYG8LWDIJHg0iwfDju2UM3LvK7s83YaPyJEPR4SYykCWYVw+4ltVdcKwv 9ldG+uKTMqJfv878T4w8xyMjJAWRJEtvG9f40jtfkfXC0b16fdAllXMOBJMiz/vPKnNZ+ WZvL/GA1meMXwJrfvc9qBkqALIp2zxjorn6yY1neqlxiriUmf1otzyxFCJjMoyhtO0E7I oP701yPCa4bXkkCATL/wU+BKO+V+szgB2+Pa1pzB65WSiTKLBX8qfJiig19Yi8IoIwfHK MtyCM7Sxl7BUG0JTCwsFRniKR/q4XRWHv2mFIAjfTp45Zw+ZaDjOeWp0w1xnRwm7lYQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794453995; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Type: Content-Transfer-Encoding; bh=kZLfCEkYNR3aTFkGE62Dpsbp4vXo3cgt1ovFL5UjwOw=; b=GTyh94gw4ndP6ETXKB1vqu8lxprmRSdLlp1GN7JX/z9IINxJBoXj7bNPPr2IALCTt/9M F8RdCueMevC4hDgmkWrNsOTv/CZ1pLXuwMTD8WtZyrN+wR9fehUJ0TWL/jPq47qiSlWAS /Gl7lVJvZZwAZf4n9wVNrnYxuR7U7W91j3I4JjxazKYNlT3QtmKO6LuFBj6wMWbeDpJ5T pA31JvmDOCF+PrAiwD3A6jzXSm2FF99df8DMOaF6OkACaK8UE2DbNv4xhs+5JsDAV03QQ Mxdpa89KQsM6dJqyhZvmCj+sp/82quZ973/wnO/COK8KEtS6UWxv1iQY9KMmsp4Seww== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="m4D/jMl7"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 95388606A321 for ; Thu, 12 Nov 2026 03:26:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=m4D/jMl7 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7882F1F00A05; Thu, 12 Nov 2026 03:26:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794453995; bh=kZLfCEkYNR3aTFkGE62Dpsbp4vXo3cgt1ovFL5UjwOw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=m4D/jMl78kXT33pL9Qzx1gnsFezNG4znPSaas/3S4iClivV/CEjJFCYxBu8+mzLvb ge2XiIizVCgt/0GzANYwbjkfxuz5Rs+YRsMqIlx4CbD6d706F6a8l/ZUpjfU3rs5OC pNzoprkfDzVKlSXBLIZLOwk6qRqZtu7xfogPf34frpUVpNb/0yoLrdr3j27B9R1GpZ 0i6LGx2r/Z3u9g7mO3HhKmFx9E1MLlm/mYxXHV5rUgVuNWSbudKzFDP76KauTzwx9z CoYgF8EBP0i6DmMG6u0JJJ9gk2xZrUDO4fhEkgof3q8bVDm7mcCnIk+yOr38iLVsvn qpi/am+CHjikA== From: Sasha Levin To: stable@vger.kernel.org Cc: "Lorenzo Stoakes (ARM)" , Andrew Morton , Luiz Capitulino , "Vlastimil Babka (SUSE)" , Pedro Falcato , "Liam R. Howlett" , Jann Horn , =?UTF-8?q?Jakub=20Mat=C4=9Bna?= , Sasha Levin Subject: [PATCH 6.18.y] mm/vma: fix expansion of VMA_MIXEDMAP_BIT VMAs Date: Wed, 11 Nov 2026 22:26:33 -0500 Message-ID: <20261112032559.1526093-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109200401-failed-6.18-8146c6478224@kernel.org> References: <20261109200401-failed-6.18-8146c6478224@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: "Lorenzo Stoakes (ARM)" [ Upstream commit 8146c6478224d8f6395c6b08a19c344a56d79867 ] Commit ca3d76b0aa80 ("mm: add merging after mremap resize") combined merging with expansion of mremap()'d VMAs, however it also unintentionally disallowed the expansion of unmergeable VMAs. Previously it was possible to expand a mixed mapping which mremap() had already ensured was a legal expansion. This is clearly seen in the mremap() logic, as it checks vma_is_fixed_mapping() to determine legality of an expansion rather than vma_can_merge(). Additionally, copy_vma() allows for a failed merge to result in a new VMA being instantiated if MREMAP_MAYMOVE is specified. However, this is not attempted, as a failure in vma_merge_extend() is assumed to be an -ENOMEM failure. Since vma_merge_extend() is used exclusively by mremap() to perform a merge and/or expansion, resolve the issue by invoking vma_expand() for unmergeable VMAs there. Explicitly assert that the VMA is both non-fixed and a mixed mapping. This provides double insurance against broken changes in future. Note that khugepaged_enter_vma() (which vma_merge_new_range() runs) is redundant in this case, as a mixed mapping is not subject to khugepaged. Also update the VMA userland tests to add a required predicate. Link: https://lore.kernel.org/20261023-vma-expansion-fix-v1-1-6142baf1f46b@kernel.org Fixes: ca3d76b0aa80 ("mm: add merging after mremap resize") Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Reported-by: Luiz Capitulino Closes: https://lore.kernel.org/all/20261023023106.515365-1-luizcap@redhat.com/ Acked-by: Vlastimil Babka (SUSE) Reviewed-by: Pedro Falcato Cc: Liam R. Howlett Cc: Jann Horn Cc: Jakub Matěna Cc: [ sashal: replaced newer VMA helpers with equivalent vm_flags checks using the existing is_vm_hugetlb_page() helper ] Signed-off-by: Sasha Levin --- mm/vma.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/mm/vma.c b/mm/vma.c index 8669da66edc5c..6f9e3d0c2681c 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -1770,12 +1770,28 @@ struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi, struct vm_area_struct *vma, unsigned long delta) { - VMG_VMA_STATE(vmg, vmi, vma, vma, vma->vm_end, vma->vm_end + delta); + const bool can_merge = !(vma->vm_flags & (VM_PFNMAP | VM_DONTEXPAND | + VM_MIXEDMAP)) && + !is_vm_hugetlb_page(vma); + const unsigned long start = + can_merge ? vma->vm_end : vma->vm_start; + VMG_VMA_STATE(vmg, vmi, vma, vma, start, vma->vm_end + delta); - vmg.next = vma_iter_next_rewind(vmi, NULL); vmg.middle = NULL; /* We use the VMA to populate VMG fields only. */ - return vma_merge_new_range(&vmg); + if (can_merge) { + vmg.next = vma_iter_next_rewind(vmi, NULL); + return vma_merge_new_range(&vmg); + } + + /* Mixed mappings are permitted to be expanded, not merged. */ + VM_WARN_ON_ONCE(vma->vm_flags & (VM_PFNMAP | VM_DONTEXPAND)); + VM_WARN_ON_ONCE(!(vma->vm_flags & VM_MIXEDMAP)); + vma_prev(vmi); /* Reposition to start of VMA. */ + vmg.target = vma; + if (vma_expand(&vmg)) + return NULL; + return vma; } void unlink_file_vma_batch_init(struct unlink_vma_file_batch *vb) -- 2.53.0