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=1794049898; b=rtM4r9usE7YTvDTFoYHe+VQeyTQsw8I+Kp+l87JY6nLGKGE9kE5efWQLFIGSHLgpTmUR +RLpILbBOhD7tUuvRZTu23po2k0m41JXy7TCdUgwEu132e3khyYI3dcKzCqU5Eiex/2+W SGek+zWsF/mExSRDMF9wxov6CC5LOyiTPjT61oFo0f8I0R+QrLuioaawy2gfvmmI3+Jbt goOzSLfwrD/J9kquJHjEK1hXEhhfpPlec9PISMBpL8D3rqoIVG7aD6y6vUKWDK1Zt6bBE YGRQ6fleor62LqNkXCwvIIcBYFDwavl+EUu3Zx8JmCAQxrHaZ/igzgLGAokzcB+wJHg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794049898; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=MRO6dTK4+lqeeE60ar6VrsN0Zp+VOk79y+mD+ttNTOs=; b=BgCWMp1a7GCMOjb4mRY6IStXEp1/aSekLNTqDfE74oS0VyCDPtMImSIXuEavvWY7kF+m q3jyHdyW+CIYEyV+YtJWqtPqe4/OeoHN6pgNnl69mRO8x+hWdspDFH2SVIbo01MJQNOIH xLb8WdovBv3nEwnbEwl8411z4hu3MxHtT+dAirNFlFOpi9xX6m+wr8VaZ5FUWBGTHl5/H rKSVY9yfq2uQxm0K+akFwHGZboktuI0jpdIIjrg6Yd0sDDNzf+s5U9yO4HJV68QySncsf RHLHInDCITSZXs2xr7dWJOoZOGdpsRN5K0JPkkHMltBs2DtTGb+K3euBQwA6V07Bdtw== 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=JN8ZeNqU; 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 9119A606A330 for ; Sat, 7 Nov 2026 11:11:38 +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=JN8ZeNqU Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9AF021F008A4; Sat, 7 Nov 2026 11:11:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794049898; bh=MRO6dTK4+lqeeE60ar6VrsN0Zp+VOk79y+mD+ttNTOs=; h=From:To:Cc:Subject:Date; b=JN8ZeNqUvzYWTubxUHjVmdUquve8XOW/98uI3CSkjCFb2v4gjHre4NJS2mroNBUrb cOQAZnpqMtIEig6M/qFgsI9f277ncy9Crlwu8WXUPBULFEio3KShpiajXw/f9zP73T Q6Hd9U7uReQ+TqTttWCCIi0CM5Rdao7Vx1He85IOTe49py0njp/zDPY3uEn3mV6QQ5 +6LCJr7OcF+aPtozQWSgz57I27u6NDdFJ1gJ57WTCvx6WUVVyX4fDkn2GxJGCe/CEA jq1DnbZlkAwfGQQtpun8ssJej4gvvGuADsM4zZ8l8NQlefTA8NosZ1L91XeWvP1SRZ rZWif+2e5uxbQ== 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 5.15-stable tree Date: Sat, 7 Nov 2026 06:11:36 -0500 Message-ID: <20261107061136-failed-5.15-3ae91e3079b1@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 5.15-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-5.15.y git checkout FETCH_HEAD git cherry-pick -x 3ae91e3079b1504ef162b2884454d5f1421f4eb9 # git commit -s git send-email --to '' --in-reply-to '20261107061136-failed-5.15-3ae91e3079b1@kernel.org' --subject-prefix 'PATCH 5.15.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