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=1792768661; b=1hUK2+fIIurX9QSRHIspP9KCbnnv6e7Zs7LRNtP+li8RdoHI54kzaKAaa2/qNtHt6Bi7 Z+JTzV81siEAORUFf5MTvZ7BG+Tuc85q2rrps0nT7GCh7QF4Rv5yFJfGjxZ2rKLJVhfQw nWpucyOulaAnvV4E6iX4Em8l+Gxhj1XbJZvZSxaZl7MtqVhVa5CaznJm1UUAmUp1mrJHy +PY6BbRzg4CsPppgN5ZMfQP4FXBkPoPIEVSFQHqAWH8imH0tVMiPYA3z0/nwO5Fuuoh3M Ns1XQLq/x3TEeBR+TcVz/82OATzcgb7BmDEKAqjxV/pbzjGnEvbpPUgSSlBnFvIsgTw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792768661; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:X-B4-Tracking:X-Change-ID:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=9oPHb6UkUAuCeIoTZhGqRaYjHQ33ICgDmbmBczj7A+U=; b=GpOAwcSYPollOmEP9ekGU6A4gQtGC85CI2Z9/mO0gfjHxaRHxnBkmwKJbfPE2n2IQR2F /Vgpf6YQtsTPy/wxL19R7xM1/txlM4bGFKc2xf8wagwxHvZqiLhwS/d9CaC+jJgkWQs6m qZmHGUg0sBUnKQxrxbi/wbZwmlAxW5llO0ZUF4XcX+HzHiGGwSXUXdPWn1uEa/x43MSda QT+g2JHwd59xbshgzcnT15mNQZSw7Ps4RCz5o2w4pXY6/J/JNmdZOVAzj5Yatu6WnQc+T hXV0ibF8aChOgBkZ7tZAVMgkSSh3lByBpO2p+gOfnpSgWQQxHIhhHdWzb532WGIWqgQ== 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="TSVb0oU/"; 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 81251606A31D; Fri, 23 Oct 2026 15:17:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=TSVb0oU/ Received: by smtp.kernel.org (Postfix) with ESMTPSA id A21221F01825; Fri, 23 Oct 2026 15:17:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792768661; bh=9oPHb6UkUAuCeIoTZhGqRaYjHQ33ICgDmbmBczj7A+U=; h=From:Date:Subject:To:Cc; b=TSVb0oU/0DYQRlWKzFZ1+M5bfA2fsQELDWZJ7ouo4RY+HG3qghgtFgLKhqqlv0q+w jB4rnZVo6YJeBeCxsIDdByS+TqolKBBNMCYKJL+Wg9QpzxNmlkADIdv1OM9cMW1tHj NEkDqxR6G+9DmGSlP6t3axYabc4WyRwFsDEZXaWFkrzSIKa6lA7iKMGvdEcrki9PUz udtcCGV5Bh/Nxzv922razMhC95ZeyqgJwYiGq/txLyPgiMRNd5cUcwquHojkdaeNnP i5CDcxvz+pf1v5NsqSIw++7RgdM3orkRbpc8nrbLZAYqA1uUMQCYkKZe0sp0P26yLa qdbdTKswvKnFQ== From: "Lorenzo Stoakes (ARM)" Date: Fri, 23 Oct 2026 16:17:31 +0100 Subject: [PATCH] mm/vma: fix expansion of VMA_MIXEDMAP_BIT VMAs X-Mailing-List: linux-kernel@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: 7bit Message-Id: <20261023-vma-expansion-fix-v1-1-6142baf1f46b@kernel.org> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDIzNDAyNj3bLcRN3UioLEPJBK3bTMCl0zCxNjY0tDQ3PzZBMloL6ColSgMNj M6NjaWgBsDj5AYwAAAA== X-Change-ID: 20261023-vma-expansion-fix-6843391177c4 To: Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , =?utf-8?q?Jakub_Mat=C4=9Bna?= Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, ljs@kernel.org, Luiz Capitulino , stable@vger.kernel.org X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=3534; i=ljs@kernel.org; h=from:subject:message-id; bh=5ZqmiLxzSYfJofiKd8XjWTm3Ne0Gvwb77tpCkLEm588=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLJuV/XP8VY5dce4c5ahhBbniy2r97RPebTxewuXi01+y XmBsoZ9HaUsDGJcDLJiiizPv4jvDxIJm9d5wd8NZg4rE8gQBi5OAZiIcxvDP32LqMqwvT8m+k7g Dk74+9X2QX6V2JT8hYe0b0Vy87/Tq2H4K+bKsElzzaLlmUa9rDbGspysSwJWbpPzitY1MhWdp1L CBAA= X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 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. Reported-by: Luiz Capitulino Closes: https://lore.kernel.org/all/20261023023106.515365-1-luizcap@redhat.com/ Fixes: ca3d76b0aa80 ("mm: add merging after mremap resize") Cc: stable@vger.kernel.org Signed-off-by: Lorenzo Stoakes (ARM) --- Confirmed that this fixes the repro and passes mm selftests and the VMA userland tests. --- mm/vma.c | 19 ++++++++++++++++--- tools/testing/vma/include/dup.h | 5 +++++ 2 files changed, 21 insertions(+), 3 deletions(-) diff --git a/mm/vma.c b/mm/vma.c index 1be613044b4a..88ef92ab24ec 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -1851,12 +1851,25 @@ 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 unsigned long start = + vma_can_merge(vma) ? 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 (vma_can_merge(vma)) { + 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_is_fixed_mapping(vma)); + VM_WARN_ON_ONCE(!vma_test(vma, VMA_MIXEDMAP_BIT)); + 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) diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h index f449129ea97a..e0eab4eca998 100644 --- a/tools/testing/vma/include/dup.h +++ b/tools/testing/vma/include/dup.h @@ -1727,3 +1727,8 @@ static inline bool vma_flags_can_merge(const vma_flags_t *flags) */ return !vma_flags_is_hugetlb(flags); } + +static inline bool vma_can_merge(const struct vm_area_struct *vma) +{ + return vma_flags_can_merge(&vma->flags); +} --- base-commit: 2bba28e98578de622ef307d00875aa8f8bca3d10 change-id: 20261023-vma-expansion-fix-6843391177c4 Cheers, -- Lorenzo Stoakes (ARM)