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 155117CF07; Wed, 24 Jan 2024 14:28:33 +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=1706106514; cv=none; b=rMHRYSdYHWECc/EzFapqQngMP2+lGWNuaYgbnrOVWt8pYb3z60ATovZade05QoQHuEBDWIhQKOLt4y6A7PJaucgqxiMxmwmeTGWreXp6YbuSsl8Gi6XWMFGJaOtkBWWNx7/fUm9qS3J/phJdUT7+63a4RJ0AZAS7Y9cBaSwboJg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706106514; c=relaxed/simple; bh=+qlLwOJdjpq6kAvTrgjUE93HI6aqQtx2W3k1oDhQX4Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fgorKo5Py5y/ZRh5gKXlA0XGh+LRetDjNV0gLLG5kqnu4qYzBBvZv06JTvLcTUonp3jSZUJhqRk4b0KmxcafOmbnRsnqmm0yqL7Z0Lbl9OUiwq/ba7gPSh+aAKAqt9RvEKjdC2MXWnSzKXYyDm7fn/+kSf3YmszjSocaTKrqzM8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WJhF0Gb2; 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="WJhF0Gb2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A44DDC43601; Wed, 24 Jan 2024 14:28:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706106513; bh=+qlLwOJdjpq6kAvTrgjUE93HI6aqQtx2W3k1oDhQX4Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WJhF0Gb2oRzpVbskHCoqylNrPZfnEjwiCgwWzCriBnW+6ALij6e6Dl1tIdJCaOtZR 1PpJ/B30CIBnfZF96GCft46WoHHKOgk0Tp6ZyQasKqY4KEO1jAr3BNkdzbwcsnRb2p YAmw2xi1j7FkoHSxywicLR/fXjaRh36rj1I35vYEq9PQbLLeA+IbOXZ4YSuqF/jUGf nB8GxYN9qgPLUv9T6TBgAcWqPyO5b5tP7grONlyUmP7n23TbAwZvxbZmiFdj84iw+0 NU/xrrHXOfN9OXDO3vf7m/WfMrYOGRSHNALfmuEf552R0w+Qx8fsm4lD7RWWSlf21I uD4VgUbZgWXJw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Benjamin Berg , Richard Weinberger , Sasha Levin , anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net, linux-um@lists.infradead.org Subject: [PATCH AUTOSEL 6.7 04/13] um: Don't use vfprintf() for os_info() Date: Wed, 24 Jan 2024 09:27:57 -0500 Message-ID: <20240124142820.1283206-4-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240124142820.1283206-1-sashal@kernel.org> References: <20240124142820.1283206-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.7.1 Content-Transfer-Encoding: 8bit From: Benjamin Berg [ Upstream commit 236f9fe39b02c15fa5530b53e9cca48354394389 ] The threads allocated inside the kernel have only a single page of stack. Unfortunately, the vfprintf function in standard glibc may use too much stack-space, overflowing it. To make os_info safe to be used by helper threads, use the kernel vscnprintf function into a smallish buffer and write out the information to stderr. Signed-off-by: Benjamin Berg Signed-off-by: Richard Weinberger Signed-off-by: Sasha Levin --- arch/um/os-Linux/util.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/arch/um/os-Linux/util.c b/arch/um/os-Linux/util.c index fc0f2a9dee5a..1dca4ffbd572 100644 --- a/arch/um/os-Linux/util.c +++ b/arch/um/os-Linux/util.c @@ -173,23 +173,38 @@ __uml_setup("quiet", quiet_cmd_param, "quiet\n" " Turns off information messages during boot.\n\n"); +/* + * The os_info/os_warn functions will be called by helper threads. These + * have a very limited stack size and using the libc formatting functions + * may overflow the stack. + * So pull in the kernel vscnprintf and use that instead with a fixed + * on-stack buffer. + */ +int vscnprintf(char *buf, size_t size, const char *fmt, va_list args); + void os_info(const char *fmt, ...) { + char buf[256]; va_list list; + int len; if (quiet_info) return; va_start(list, fmt); - vfprintf(stderr, fmt, list); + len = vscnprintf(buf, sizeof(buf), fmt, list); + fwrite(buf, len, 1, stderr); va_end(list); } void os_warn(const char *fmt, ...) { + char buf[256]; va_list list; + int len; va_start(list, fmt); - vfprintf(stderr, fmt, list); + len = vscnprintf(buf, sizeof(buf), fmt, list); + fwrite(buf, len, 1, stderr); va_end(list); } -- 2.43.0