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=1794435132; b=PbunCwM/6qcy0rpN8F+TK+zUKQYu3GjCOqWXkNIpeqXDf1wrCp+9EqyK4n0nM1ybeHU4 jy55id9qXXIkBhwsEULeC4siObdjaanWZIQTh3bpYqxWQLfkYZjnVNzTJfdPWvLDffPOk SKCW5UvcDgBFAc2PslcqArwk17ElwtTtdSa7D9v++wrRIi8h2Yl8BlqaxAiI+wmK5AigB jEPgyunoC8sv+nDmFPn0SyMLAvNUskI2NQ6istF3mu5wOgIHDtTBWS9m5RXQQCZdW+tRt kknJGV8Je2FBTEtqaUaPL0r3kQpjkAj94OFhsHXphTxVdToS14VpbPxSFbBdgdrSLiA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794435132; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=HoWw2LtXhaLTvRjoyzf/GLGky1XfPZvo/+Hksni2ztQ=; b=akrcSOZ+WdrluTjKLo0D9ofCQrFklC5mITwnRWrkUThkT6HUlN314QV1rGDcTP/1mK57 1r7aH75T2RMWewxCAiVuflQpIp+J7s/kjIzcBNlJ2WpIxX3SmBpG/n7iBJRW+pClS8xmB uVe320BCQknpDpvFiJ3Fnjweb4w9jzKuyyu3TL9MZEiPxcc/rmYmwISyjVEWVkPzf1hmv YBk54spkhkKQxLJT/0lAW98wey9XZntrb3wAPnY5DIBguOLyhG6f2wwM3Q1zXSTMOlH8G xw4VupPAw5qcOVk+qxCxzjcZNlK85sFsifVhn+LKHlhv05kb6U83s29pQn/Ei3UxuhA== 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=RtPj7j4P; 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 B33EB606A326 for ; Wed, 11 Nov 2026 22:12:12 +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=RtPj7j4P Received: by smtp.kernel.org (Postfix) with ESMTPSA id CC5E51F00A06; Wed, 11 Nov 2026 22:12:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794435132; bh=HoWw2LtXhaLTvRjoyzf/GLGky1XfPZvo/+Hksni2ztQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RtPj7j4Psimqti6/xGiGh5TQTkwBE1kSPeObTtnGvVjIy8V9aGraO6wBcClRYXk1C wKifGB3fsxvR9Ho399CWGu6PaHFnAeUbVnPI8Aw8vG0QldmPvxUCUIrCl7rrzLBf0d zxilndnxnGEKr4P47Tymmbxad0bTg7y/Jn/AzjAcMEW9wa8lsXzgXp7cw7V+k5fpGJ BddKIFzp5WtaaSHL4NDCcXNo8GL1OxN/V9t4jTWBjv/K2A4A9gLKcXqyuDAl1B5UnQ /vhx2DpUPjHVdtZ7AnJd562kDpbyZSgCcW0tP/EH+RhwB0hHj5Yq/yQSSQ3cQBPOzA qYzV5LqIb+uXg== From: Sasha Levin To: stable@vger.kernel.org Cc: Konstantin Khorenko , Eva Kurchatova , Andrew Morton , Shuah Khan , Wei Yang , Sasha Levin Subject: [PATCH 5.15.y 2/2] selftests/core: fix unshare_test with large fs.nr_open Date: Wed, 11 Nov 2026 17:12:09 -0500 Message-ID: <20261111221154.4123375-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261111221154.4123375-1-sashal@kernel.org> References: <20261107060233-failed-5.15-df0b7e0ea59c@kernel.org> <20261111221154.4123375-1-sashal@kernel.org> 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-Transfer-Encoding: 8bit From: Konstantin Khorenko [ Upstream commit df0b7e0ea59c43708cff8c7e34da5e2f8d430e5e ] The test assumes fs.nr_open is close to the default 1048576, but some systems set it much higher (e.g. 1073741816). This is systemd's doing: since systemd v240 (2018), PID 1 bumps fs.nr_open and fs.file-max to their largest possible values on boot, as file descriptors are already accounted for by memcg [1]. In that case, dup2() to nr_open + 64 requires the kernel to allocate a file descriptor table with ~1 billion entries, which fails with ENOMEM. On a kernel that already carries 04a2c4b4511d1, dup2() no longer fails with ENOMEM. The allocation is now rejected up front and the caller gets EMFILE instead, without the WARNING, but the test still fails. Cap the nr_open value used for the test's own arithmetic to a known reasonable base value (1048576) and restore the true original value once the test has completed. Link: https://lore.kernel.org/20260814165709.513263-1-khorenko@virtuozzo.com Link: https://github.com/systemd/systemd/commit/a8b627aaed409a15260c25988970c795bf963812 [1] Signed-off-by: Konstantin Khorenko Signed-off-by: Eva Kurchatova Signed-off-by: Andrew Morton Cc: Shuah Khan Cc: Wei Yang Cc: Signed-off-by: Sasha Levin --- tools/testing/selftests/core/unshare_test.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/core/unshare_test.c b/tools/testing/selftests/core/unshare_test.c index 7fec9dfb1b0e3..6716e0f74d7da 100644 --- a/tools/testing/selftests/core/unshare_test.c +++ b/tools/testing/selftests/core/unshare_test.c @@ -40,6 +40,14 @@ TEST(unshare_EMFILE) ASSERT_EQ(sscanf(buf, "%d", &nr_open), 1); + /* + * Cap nr_open for the duration of the test to avoid ENOMEM from a + * huge fd table allocation; buf/n keep the real original value so + * fs.nr_open can be restored to it once the test is done. + */ + if (nr_open > 1024 * 1024) + nr_open = 1024 * 1024; + ASSERT_EQ(0, getrlimit(RLIMIT_NOFILE, &rlimit)); /* bump fs.nr_open */ @@ -73,10 +81,13 @@ TEST(unshare_EMFILE) if (pid == 0) { int err; + char buf3[32]; + ssize_t n3; - /* restore fs.nr_open */ + /* restore fs.nr_open to the (possibly capped) test baseline */ + n3 = sprintf(buf3, "%d\n", nr_open); lseek(fd, 0, SEEK_SET); - write(fd, buf, n); + write(fd, buf3, n3); /* ... and now unshare(CLONE_FILES) must fail with EMFILE */ err = unshare(CLONE_FILES); EXPECT_EQ(err, -1) @@ -89,6 +100,10 @@ TEST(unshare_EMFILE) EXPECT_EQ(waitpid(pid, &status, 0), pid); EXPECT_EQ(true, WIFEXITED(status)); EXPECT_EQ(0, WEXITSTATUS(status)); + + /* restore the real fs.nr_open value */ + lseek(fd, 0, SEEK_SET); + write(fd, buf, n); } TEST_HARNESS_MAIN -- 2.53.0