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 B63057C089; Wed, 24 Jan 2024 14:29:21 +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=1706106562; cv=none; b=UPVotcQVgWdJqP4edJPbaPOT/D91RlB/qxB9da+7fLZe6ZJdGKG6j1LPJXMk9jLkICGoBzjkWDBWkOUPh7KPlF7Q7tC5l6D738eQLD7BgpoQDPMzOEMpdwDQMIiRDwGDsAUyrJCXFpKEOE28UBozvH7NtavrtBJPmriiM6UnR3M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706106562; c=relaxed/simple; bh=+qlLwOJdjpq6kAvTrgjUE93HI6aqQtx2W3k1oDhQX4Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WXnXiCMadOumDu8Dta1eVbHuhdtt4gM050cQYwTJtTN/TUBuPXuWgV8vQmcU4rsTGJZTRne9Mb2OCAfF80TnAVcmMXF3jKaFXmqz0yH+kc1FbU2m9OqmuRP1PGwAttzlzm8L24Ly45jzO78cUl5q380IlO9IEe+3WqKe4ObwmyE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=E1pXuPNE; 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="E1pXuPNE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C735C433F1; Wed, 24 Jan 2024 14:29:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706106561; bh=+qlLwOJdjpq6kAvTrgjUE93HI6aqQtx2W3k1oDhQX4Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=E1pXuPNEs/XjGlr6b3iLInMoiSZuH+6ZxaEhS8RE5ZThQrCwOrYgOB4bSgl83Fyl1 ANZ6HljjnQxMaN1N1QhSTRnzH+L0mHeATfPAbXoZtwyXhLlO7h/4d77cUppJ4qi6Ro Y6qx9cHeRiklETSRo5fx//NZ522qLqex4qUKtRG/j53SDIevhh6ft/tws+MFD9ub5x 8RpYwk1MDHewAH4uGgbMW/pcUwHZvOrY8fuhyqAUXszetAwLyCK29fKbt5Ea2op/ks DVxZvYJytRp7qP/QV43KQkvRS3ZgAsQoPooPOsJYQ7hkHHGhx4yoCAUKhwpMwATq/5 C7bcaAwGrsHvQ== 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 6.6 04/11] um: Don't use vfprintf() for os_info() Date: Wed, 24 Jan 2024 09:28:47 -0500 Message-ID: <20240124142907.1283546-4-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240124142907.1283546-1-sashal@kernel.org> References: <20240124142907.1283546-1-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 6.6.13 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