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 3D9D0435EEC; Fri, 7 Aug 2026 14:49:47 +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=1786114188; cv=none; b=UT+l+fdzBA/lZtiyVJTITEclvej4SXQqCD7j44C66GTpAGXJvHB8KEMkxgh0GRU1+T8yqjzzQMj5S5bdvfgLPFvxCKriSHI9HHXf/FhnKz740IyeJDyQZzSyS/7cQtca4L8v/E9JdRUmziydtyllHJKPEXRxdfaOf8/bkAYubTY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786114188; c=relaxed/simple; bh=Vry3ypEbA0fJBGKrK7g3B4EjyLnt7eDxPaouj5l8rhE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JbUlOdExS5uYv9iYegXcnqtAq8kUzdiunad4tQe6kI1Jyr58JyYUBH8akvOvVzfoLG1nbRtfVuhc8/vdXz69QvUAz8g0hAtY02yh66rDcjGW691eDdlHRD8t/MVfYZ/WXlcPPNG3BGBZEVSJlVqtyP4WdJAMbf5dRIOHpIrgMfo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zjIwjTs7; 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="zjIwjTs7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 973A21F00A3A; Fri, 7 Aug 2026 14:49:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786114187; bh=ye2Lp1dSHOVinOhXEYb/mxjzYzsAgED++5voB7j2V4M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=zjIwjTs7NqOAFiJuy9c0E+KYl4eakbaWVHSOfRhOr8YcQFfoiKTqs+CueFQ2SplUg JR8JPtp+UNgfkLQ0BpBMZCAK5iVBaINWig/5qJVenxcciQ4dNnRsXrpoYyVhjZgLf4 7hojcP+IiCm8NuIctR40foz0k/i6Z9kYPbVQeKYQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Michael Bommarito , Gao Xiang Subject: [PATCH 6.12 131/337] erofs: cap LZMA stream pool size Date: Fri, 7 Aug 2026 16:35:34 +0200 Message-ID: <20260807143421.373614133@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260807143418.516897842@linuxfoundation.org> References: <20260807143418.516897842@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Michael Bommarito commit c9b47e6b23114e939b17f818471c7a46e59006e7 upstream. fs/erofs/decompressor_lzma.c sizes the module-global MicroLZMA stream pool from num_possible_cpus() when the lzma_streams module parameter is unset, then z_erofs_load_lzma_config() preallocates one image-supplied dictionary per stream, accepting dictionaries up to 8 MiB. On high-CPU systems, a small EROFS image can pin hundreds of MiB of vmalloc-backed decoder state until the erofs module is unloaded. Impact: An EROFS image mounted by the system can pin up to 8 MiB of vmalloc memory per LZMA stream, either as intended or unexpectedly. Bound the default stream count by a new CONFIG_EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS option, default 16, so the worst-case default preallocation is 128 MiB if the number of CPUs is no less than 16 while preserving the existing per-image dictionary limit. An explicit lzma_streams module parameter is still honoured as-is, so administrators who deliberately size the pool are not affected. Fixes: 622ceaddb764 ("erofs: lzma compression support") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Michael Bommarito Reviewed-by: Gao Xiang Signed-off-by: Gao Xiang Signed-off-by: Greg Kroah-Hartman --- fs/erofs/Kconfig | 14 ++++++++++++++ fs/erofs/decompressor_lzma.c | 3 ++- 2 files changed, 16 insertions(+), 1 deletion(-) --- a/fs/erofs/Kconfig +++ b/fs/erofs/Kconfig @@ -114,6 +114,20 @@ config EROFS_FS_ZIP_LZMA If unsure, say N. +config EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS + int "EROFS LZMA default maximum decompression streams" + depends on EROFS_FS_ZIP_LZMA + range 1 NR_CPUS + default 16 + help + By default EROFS allocates one LZMA decompression stream per CPU. + Each stream can hold a dictionary of up to 8 MiB taken from the + mounted image, so on systems with many CPUs this can reserve a lot + of memory. This caps the default; the lzma_streams module parameter + still overrides it. + + If unsure, keep the default of 16. + config EROFS_FS_ZIP_DEFLATE bool "EROFS DEFLATE compressed data support" depends on EROFS_FS_ZIP --- a/fs/erofs/decompressor_lzma.c +++ b/fs/erofs/decompressor_lzma.c @@ -51,7 +51,8 @@ static int __init z_erofs_lzma_init(void /* by default, use # of possible CPUs instead */ if (!z_erofs_lzma_nstrms) - z_erofs_lzma_nstrms = num_possible_cpus(); + z_erofs_lzma_nstrms = min_t(unsigned int, num_possible_cpus(), + CONFIG_EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS); for (i = 0; i < z_erofs_lzma_nstrms; ++i) { struct z_erofs_lzma *strm = kzalloc(sizeof(*strm), GFP_KERNEL);