From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 929242F8EBB for ; Sat, 9 May 2026 12:26:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778329572; cv=none; b=N3WityUY8cHXALbZKCboRCAEajYXWyvtOmN2e7bllMXqcY+96TrXTS1TkjUm4zxbWbay0mWLwWi/PfkGVp3D90Bou4Z4O56+mFFLI6d5+jybgZDW7D5nWyYkN9T0lMa1csYpWdXxcYQtCzif2s+y8g+aJ/CILp7qGDL7u8MkX98= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778329572; c=relaxed/simple; bh=+x+gvK5ltyMW+xQryPieVZ4ulyohqWR8VazO1gtHFJQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UtVxK0cnjxCsEFpXyYjNv1udSD1sJTBVHz/54SHOjUqIyG+DpKHYLoXx8uemzqn5yX/Zm1Fg13Y/GpdktQA5eJzvSImRj3EAvZl68p/2DanwCtV1mao6BAVwv7Oiz1qIKn4rm/GJHI3LUlVwvITToWAn5aAAQrCgEQceCylRGYI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QWWsxqq9; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QWWsxqq9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9D689C2BCB2; Sat, 9 May 2026 12:26:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778329572; bh=+x+gvK5ltyMW+xQryPieVZ4ulyohqWR8VazO1gtHFJQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QWWsxqq9WShW7QDagg1YwnnRvN5rOOQC4/ZTgn5bhUd/9ItSK1seCMoXJfHQM1npI 03UFNixCpRpH3Q2abBw3mk58EB13ALRDAB/mGf4n+sZWrpeJRsB7smOXBVsFRGMwAU Xk366q45NNCKZkLSCye03jae9Ma1oV2sixMJIi4ey8oFvDVHNe7/aSjhNa1/41zwzC jLGuNwffrTu6UwaauhA4el7CmdXw10WYh7Rhf4l+fZohqegZYiLM+L85vdn03FU3Ek 5z07I6hjBqRpE4+P9DAgFSKxYjCsNFB5MS/3hl69Q0isuEkI/ILKsXed+DICixnnYg LwOu1Xi7X/83A== From: Sasha Levin To: stable@vger.kernel.org Cc: Junrui Luo , Yuhao Jiang , Gao Xiang , Sasha Levin Subject: [PATCH 6.1.y] erofs: fix unsigned underflow in z_erofs_lz4_handle_overlap() Date: Sat, 9 May 2026 08:26:09 -0400 Message-ID: <20260509122609.3351909-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026050415-daydream-unopened-fa80@gregkh> References: <2026050415-daydream-unopened-fa80@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Junrui Luo [ Upstream commit 21e161de2dc660b1bb70ef5b156ab8e6e1cca3ab ] Some crafted images can have illegal (!partial_decoding && m_llen < m_plen) extents, and the LZ4 inplace decompression path can be wrongly hit, but it cannot handle (outpages < inpages) properly: "outpages - inpages" wraps to a large value and the subsequent rq->out[] access reads past the decompressed_pages array. However, such crafted cases can correctly result in a corruption report in the normal LZ4 non-inplace path. Let's add an additional check to fix this for backporting. Reproducible image (base64-encoded gzipped blob): H4sIAJGR12kCA+3SPUoDQRgG4MkmkkZk8QRbRFIIi9hbpEjrHQI5ghfwCN5BLCzTGtLbBI+g dilSJo1CnIm7GEXFxhT6PDDwfrs73/ywIQD/1ePD4r7Ou6ETsrq4mu7XcWfj++Pb58nJU/9i PNtbjhan04/9GtX4qVYc814WDqt6FaX5s+ZwXXeq52lndT6IuVvlblytLMvh4Gzwaf90nsvz 2DF/21+20T/ldgp5s1jXRaN4t/8izsy/OUB6e/Qa79r+JwAAAAAAAL52vQVuGQAAAP6+my1w ywAAAAAAAADwu14ATsEYtgBQAAA= $ mount -t erofs -o cache_strategy=disabled foo.erofs /mnt $ dd if=/mnt/data of=/dev/null bs=4096 count=1 Fixes: 598162d05080 ("erofs: support decompress big pcluster for lz4 backend") Reported-by: Yuhao Jiang Cc: stable@vger.kernel.org Signed-off-by: Junrui Luo Reviewed-by: Gao Xiang Signed-off-by: Gao Xiang [ inverted condition to early-out `goto docopy` form and used `ctx->inpages`/`ctx->outpages` instead of `rq->` ] Signed-off-by: Sasha Levin --- fs/erofs/decompressor.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c index e524c0b432f39..a63522e84fe0a 100644 --- a/fs/erofs/decompressor.c +++ b/fs/erofs/decompressor.c @@ -133,6 +133,7 @@ static void *z_erofs_lz4_handle_overlap(struct z_erofs_lz4_decompress_ctx *ctx, if (rq->inplace_io) { omargin = PAGE_ALIGN(ctx->oend) - ctx->oend; if (rq->partial_decoding || !may_inplace || + ctx->outpages < ctx->inpages || omargin < LZ4_DECOMPRESS_INPLACE_MARGIN(rq->inputsize)) goto docopy; -- 2.53.0