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 C42D83CF42; Wed, 21 Feb 2024 14:04:55 +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=1708524295; cv=none; b=TMDKrNO/rsy65yclp2qc3H/BmmMb0WqQSl5oQVfeY1nD08/MU/kEVgiLT2skU/LTykVmwxhh/KCGfaY3pOAzQ/zc+esuIe4icVKcc439P4o1YYmxesiJyPxqqOqzo/uN3JiEQIsCUnCnYHss4CpnzbQdyE3PU0rHiBqQXLLjfN0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708524295; c=relaxed/simple; bh=h58a0AMHIHy4ffpmaHSfHk60wkwWl+kwvevWmeSTF3w=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KXzeGFZPa5khAoc6lpY2hY3NFAR+WcnV8K9e2BVLQUFmz6jlQMlA/81RQtvfpAkTWA3b+yz0cxIzVFEokKwJir/4xUMLP85n4drO8wSXt0B7gFO845kYfjysr/edNjVFKeePW+3rrcO/af9Pudt6QKcXKiEM5NxBRZUUXYjjKEw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=MKY5KOgb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="MKY5KOgb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 35D13C433C7; Wed, 21 Feb 2024 14:04:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708524295; bh=h58a0AMHIHy4ffpmaHSfHk60wkwWl+kwvevWmeSTF3w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MKY5KOgbxNu8gGtG3lG2TvHvc0X+VQ1LMAGw1Hlcza6IPcS7O8Xu4ghd5H3wstz/8 QRrhAo/xE3x/GvOwlrPiA9PWWXHmO3KggkGNAZmseotOI52BAls4+YmuXtFeCDuvJU 1gl2jB5KhC/j8m0YYItJXShtgqZummwWMzr7ts38= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Benjamin Berg , Richard Weinberger , Sasha Levin Subject: [PATCH 5.10 202/379] um: Dont use vfprintf() for os_info() Date: Wed, 21 Feb 2024 14:06:21 +0100 Message-ID: <20240221130000.878138926@linuxfoundation.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240221125954.917878865@linuxfoundation.org> References: <20240221125954.917878865@linuxfoundation.org> User-Agent: quilt/0.67 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 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ 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 07327425d06e..56d9589e1cd1 100644 --- a/arch/um/os-Linux/util.c +++ b/arch/um/os-Linux/util.c @@ -166,23 +166,38 @@ __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