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 7935D135A76; Wed, 24 Jan 2024 14:32:00 +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=1706106720; cv=none; b=bvO8TuwFpzBxF16PwUN13dcwiOMvXCCdHvn6StuOquAO7FKMmqJqvOVtor/zA27Da1/ZMXqnbjfhhCpmKQ9jRIBUju5ImcTWfT5HLrLR58bbY4QwBHikJZ02XOQf5DQYv7uvGTWwLxNmTykGE4U2ZAIkN8tIm36/JvlOQv+aVqc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706106720; c=relaxed/simple; bh=RqHq28KrRsG1sb1EQg9DKXv8hvRBmr+M1tnj8o4C0r0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kDOwrx7rewq6addgPzkIzsD+W/DNz5s6znr7Ecey064qT5duH5oTcdgOg40mFzr5IdF6Ig+SOLEUQs0DnrU2nPUs4tSco0s8lV1JWdLc5MAef/mNYGSAJ2iOGu7ktZov0R2HpVzcGEkZGnbCKIjKiYxdijiHtq7LDCUHBwW6ZUs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=tXMUN5cl; 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="tXMUN5cl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 240A6C433F1; Wed, 24 Jan 2024 14:31:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706106720; bh=RqHq28KrRsG1sb1EQg9DKXv8hvRBmr+M1tnj8o4C0r0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tXMUN5cly+xxrEFw3U0pI0Gl+IN5fc92UPB0oynjIIW5uPUGyar7abaqtNIkQwql2 AKCjXHSDuuYYDn9LQg5I4i5Yz99kWcaWG7kl7UV3l+AV7UBl2TKJttZrOSS9gRhXWk ftkcRrnCjgu8nCrq38b+xK44gX82Q3nX6W8qwpB6Zt9yMSWWBWYU+f6gZ0gBVpkYrR E++u+Q4wmlafc5iI9xdtIN+lO7j+NJC+Y/4sMoIjq4M/U6GzHrEvr2ze5kOMDWkr4P s18GvygltVWAtrsR4n6F40+yV8XtQp8YFfENmM+iU1AIoVOkSH2atNq0xDC3STzhPM M+/OJ0W5CdRIw== 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 4.19 3/5] um: Don't use vfprintf() for os_info() Date: Wed, 24 Jan 2024 09:31:38 -0500 Message-ID: <20240124143149.1284622-3-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240124143149.1284622-1-sashal@kernel.org> References: <20240124143149.1284622-1-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 4.19.305 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 8cc8b2617a67..0436cc9537e0 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