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 0BA58428470; Mon, 17 Aug 2026 14:35:33 +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=1786977334; cv=none; b=R6tkW1cltAn9aNYaLD4rfHQ/uTp1eYyFw54g6D5ZgirTSOOBsZiwvwwCFc2OMyG3FI0axQDHpA2zV5/zIX95eKPXJFkkjwwC1uK12z59HDbGlEjj/2HFnT79ZeXiF06W5K+u0lhJ0Ti7ATPimDV0yH3BgeNCf+bJt1v56Sh6G0s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786977334; c=relaxed/simple; bh=bMLLdCLdz3lxkOFiB00e75u35pR9tXlPcCKFMTdy1gc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SBWtDnEVnwbDuzYY7CQZkvb74Beyr8JcqSQMmW+3RcXlPhbMVGnA997A9xmXhMLw8ne9z8hso0jMm7NDrxqf00uZymxVBDcRvvgqciMmPkS7zzZpribrGOVFqzPwcjPUpohoavAuOeLeKWOEneYxPDQ2uohvm29rjMClEGI9pvY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Fw9meDnD; 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="Fw9meDnD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6399D1F000E9; Mon, 17 Aug 2026 14:35:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786977332; bh=xvsCLDEUIXHphndut2SV5Yk6whzvFyQ5XlQ94WTYBkE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Fw9meDnDgPEEDFojfTP0am2hUVp7YKq0rAudpscrmULmYVeaoQzyrE1D4FHgBapnw RD2lZz9mXQ3kPtSY6Mf8pUjya05+WV1wAdStcGWgZWH5SA4Px2E+x11CO4UbP+Hcur R8Bft1eSVdF4rGUa7Ktirxy6JHDirS5oVdTaxaJU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sashiko , Zi Yan , Dennis Zhou , Christoph Lameter , Tejun Heo , Andrew Morton Subject: [PATCH 5.15 293/456] mm/percpu-km: fix bitmap overflow and accounting in pcpu_create_chunk() Date: Mon, 17 Aug 2026 15:31:23 +0200 Message-ID: <20260817132551.328836956@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817132539.792407575@linuxfoundation.org> References: <20260817132539.792407575@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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zi Yan commit 89b1b79c308818a715e75f28744b70d8940a07c9 upstream. In pcpu_create_chunk(), nr_pages is the total contiguous backing allocation, i.e., nr_units * pcpu_unit_pages, but pcpu_chunk_populated() uses it to set chunk->populated, whose size is pcpu_unit_pages, bitmap. Since bit N in chunk->populated means page offset N inside every unit is backed. When nr_units > 1, the function writes beyond chunk->populated. Fix it by using chunk->nr_pages. It also fixes the global pcpu_nr_empty_pop_pages accounting, since pcpu_balance_free() only iterates up to chunk->nr_pages. Commit a63d4ac4ab609 ("percpu: make percpu-km set chunk->populated bitmap properly") introduced the bitmap overflow issue. Later, commit b539b87fed37f ("percpu: implmeent pcpu_nr_empty_pop_pages and chunk->nr_populated") added pcpu_nr_empty_pop_pages and caused the accounting issue. Link: https://lore.kernel.org/20260709-fix-pcpu_create_chunk-in-percpu-km-v1-1-1f64745a84cc@nvidia.com Fixes: a63d4ac4ab609 ("percpu: make percpu-km set chunk->populated bitmap properly") Reported-by: Sashiko Closes: https://sashiko.dev/#/patchset/20260703-keep-subpage-private-zero-at-free-v2-0-2970fe777dd6%40nvidia.com?part=1 Assisted-by: Codex:GPT-5 Signed-off-by: Zi Yan Acked-by: Dennis Zhou Cc: Christoph Lameter Cc: Tejun Heo Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/percpu-km.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/percpu-km.c +++ b/mm/percpu-km.c @@ -75,7 +75,7 @@ static struct pcpu_chunk *pcpu_create_ch chunk->base_addr = page_address(pages); spin_lock_irqsave(&pcpu_lock, flags); - pcpu_chunk_populated(chunk, 0, nr_pages); + pcpu_chunk_populated(chunk, 0, chunk->nr_pages); spin_unlock_irqrestore(&pcpu_lock, flags); pcpu_stats_chunk_alloc();