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=1794048879; b=j6FI7MrM2UAbbQnY+7CtcN0tkr1mFtI7UbLwNmey6ffR2SjXOA1XYKyUpaBuAy4T4Url oDQatm6PHzTL0l66RUp1kQ8A15GPr6KcZbDn6nm34Q5ClohvoQYvsSPTMML8Aw+btCbXz zLv6samgbLLLCpYw9BlTSEcG5+szGUUFCdQM3GIFKA2ZO5PnjNMjYHmEEFVoL6OYM+2MT cobaKFYS4mX4QWOSEkX0WswRfKnCE4iHnPFYmBVHHPSUxwKgQl0AKKIAD1h1q0lIs1hKZ trN+2VcXT4aTfuydE1V07p/9qDq9+C63LhkWvCfOXBypMhoGWWN5Obr3SmXIOdBBguw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794048879; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=JNRlRgcDMisJ+rvIeEt8VFs0t0HbphcUiC2vKlL2c0s=; b=ESAfbvoxL+cln3B9vAi8lErtxreZYzsV1+HdGHrOpN5yNjvI6mVWwoyGTJYsM7S969xL mUx4G2a3U8b+Z21lI++4r1ogIketRQuF9An+pI00Z47GV+r6o699a2Z/CWdWETH50YhZ6 6+yROiZnQfKmpjq140/uMYvaRpg6jnUgnBHoIoyqP2U0+QDi5FEZ7JEDfjIM1+UTvF4b2 45dqpaSf6Ys6gUGWbJ4ruh9wZv7ejW/dQyPLAhRIsnbzPCMGIrlHMSjB5pj7FLXd7Afb7 q/8NvTxt9cOxOClHiSh1v7sK/aRDwYEtCAJogno8R3hSHba+vwBSoJ0GjHvU973yEPw== 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=iOR3UR5S; 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 D92E4606A326 for ; Sat, 7 Nov 2026 10:54:38 +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=iOR3UR5S Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE3481F008A1; Sat, 7 Nov 2026 10:54:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794048878; bh=JNRlRgcDMisJ+rvIeEt8VFs0t0HbphcUiC2vKlL2c0s=; h=From:To:Cc:Subject:Date; b=iOR3UR5SDezjbyeClco5eQK8R3KdE6Rm2yINYBIqIfXz+cwa6oZjNARwSzPuCoVqQ kmhe0jHGiX4gZlEnodxsG6HxoNXThTIiFbnJ7E3DIiOJR5JtUyL7YuIMDTPeey2UEv gpmf0mUpzhIgODyYzT1csliJPElhUD++JAjvkCeiTttNS5jkRGcuxQE8Kb6DXr6FXp wzNWahOvzGnmmITzZO6j+IJoXMyP4I0Kwj5D0jSj/dqGauGGih+LXzTDqgcicn6fTS H5G1KvMEVVJXHGnVc3JP8/UHosTUhlAA0cRTZNoQ5ZoncyS5/Yto+rfonyFBWjcLuD 3pQ0FR3ru2rkA== From: Sasha Levin To: nickolai@csail.mit.edu, akpm@linux-foundation.org, pfalcato@suse.de, liam@infradead.org, ljs@kernel.org, vbabka@kernel.org, jannh@google.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/mlock: use a long for the page count in mlock_fixup()" failed to apply to 6.1-stable tree Date: Sat, 7 Nov 2026 05:54:36 -0500 Message-ID: <20261107055436-failed-6.1-3ae91e3079b1@kernel.org> X-Mailer: git-send-email 2.53.0 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 The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 3ae91e3079b1504ef162b2884454d5f1421f4eb9 # git commit -s git send-email --to '' --in-reply-to '20261107055436-failed-6.1-3ae91e3079b1@kernel.org' --subject-prefix 'PATCH 6.1.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 3ae91e3079b1504ef162b2884454d5f1421f4eb9 Mon Sep 17 00:00:00 2001 From: Nickolai Zeldovich Date: Wed, 14 Oct 2026 09:13:58 -0400 Subject: [PATCH] mm/mlock: use a long for the page count in mlock_fixup() mlock_fixup() adjusts mm->locked_vm, an unsigned long, by the number of pages whose VM_LOCKED state it changes, but computes that number in an int: int nr_pages; ... nr_pages = (end - start) >> PAGE_SHIFT; ... mm->locked_vm += nr_pages; When a single VMA range of 2^31 pages (8 TiB with 4 KiB pages) or more is locked or unlocked, the count is truncated to 32 bits and then sign-extended, so locked_vm is changed by the wrong amount, while munmap(), mremap() and the other paths that maintain locked_vm use the full unsigned long page count. Such a range is reachable on 64-bit architectures with a 47-bit or larger user address space (x86_64, arm64 with 48-bit VA, riscv64 Sv48) by a task with CAP_IPC_LOCK or a raised RLIMIT_MEMLOCK, which do_mlock() checks against the full untruncated length. It costs nothing with MAP_NORESERVE and MLOCK_ONFAULT/MCL_ONFAULT, since then no page is populated. On x86_64, after p = mmap(NULL, 8UL << 40, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0); mlock2(p, 8UL << 40, MLOCK_ONFAULT); VmLck in /proc/self/status reads 18446744065119617024 kB instead of 8589934592 kB; munmap() of the region then subtracts the true size and leaves VmLck at 18446744056529682432 kB instead of 0. With 16 TiB, locked_vm is not changed at all, VmLck stays 0 kB, and after the task drops CAP_IPC_LOCK or lowers RLIMIT_MEMLOCK, mlock(), mmap(MAP_LOCKED) and the other mlock_future_ok() and account_locked_vm() users enforce RLIMIT_MEMLOCK against that count, so they let the task lock memory beyond its limit (or, in the 8 TiB case, refuse every further lock). The error persists for the life of the mm; unlocking the range in pieces skews it further. The wrong count is per-mm accounting only: it does not change which pages are locked. The int has been there since before git history (the variable was named "pages" until it was renamed in 2.6.28); every other updater of locked_vm uses an unsigned long or long count. Make nr_pages a long, which holds the page count of any user range and its negation, so the existing sign handling is unchanged. Found by formal verification of mm/mlock.c against the kernel binary. Link: https://lore.kernel.org/20261014131358.780240-1-nickolai@csail.mit.edu Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Nickolai Zeldovich Signed-off-by: Andrew Morton Reviewed-by: Pedro Falcato Assisted-by: LLM Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Vlastimil Babka Cc: Jann Horn Cc: --- mm/mlock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/mlock.c b/mm/mlock.c index 4235a1518fc9e..67ae9b18b9235 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -457,7 +457,7 @@ static int mlock_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma, { const vma_flags_t old_vma_flags = vma->flags; struct mm_struct *mm = vma->vm_mm; - int nr_pages; + long nr_pages; int ret = 0; if (vma_flags_same_pair(&old_vma_flags, new_vma_flags) || -- 2.53.0