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 6A4A47E788; Wed, 24 Jan 2024 14:30:36 +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=1706106636; cv=none; b=CKXI+sh/UkVBveTtPRyQ93SNEQ56QRSEL0dMxnCMRHG4DpkzypxH15hQxzdvV+SCENLFiDC0/y/eroY/ecEvni9OGyguyl9yWbBPG3TG3QnU2yJaueCgFDnyYyV3B070nfqya6Cjm8pVBU8gLmKsRvDul0Dok53FFOg3cubCjQg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706106636; c=relaxed/simple; bh=+qlLwOJdjpq6kAvTrgjUE93HI6aqQtx2W3k1oDhQX4Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZLnQALAQQmt5cj16/IhXR3ciXVGHHKFZcvZb6FjlHjR814poTkUkPJS4nn6a5PHhEza5pgptrUu5WG6g5tOwIk74se0WRyf9wy2xwjqlH5jATl9pQOnrkUJLog0659qA+U8SPuJ9qqCp76P8DZNsZvnsEwLLc+zeekg55s6L3s0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HBZ2K9os; 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="HBZ2K9os" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 12F54C433A6; Wed, 24 Jan 2024 14:30:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706106636; bh=+qlLwOJdjpq6kAvTrgjUE93HI6aqQtx2W3k1oDhQX4Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HBZ2K9osqL2QczXrXHYBnHPo6+UU8xt/cCPoRKgFLzejPGJ58GGaRH4s2atAI6Xee Pb2Tx8g1JTbeYf/cgruFAa/xM1WE+h2JzXiDy/xpC3DhKSMH4Uw3vBh/dXthvk3BDO aBkOCkiO4MQStk/DV2tzmns5U0jU9OBQYnXDIBmN3eMR0CAbkUTUmPXljw5GwssMlx gqD8OnSlkh9UdZ3gEPuVlELNIj+71z93YnpjZcYiQ3bPBqdKyrS5p9hgJa3vyCSfch PELjHBPh0VpBq4/KCSAT+aDlsEx8wsKtoPNhi6NSwq5SyWzjKi8l/9XZ72Lb3ERZcS bTHiw0aJOfwDA== 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 5.15 3/9] um: Don't use vfprintf() for os_info() Date: Wed, 24 Jan 2024 09:30:06 -0500 Message-ID: <20240124143024.1284046-3-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240124143024.1284046-1-sashal@kernel.org> References: <20240124143024.1284046-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.15.147 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