Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756401Ab1CMCUH (ORCPT ); Sat, 12 Mar 2011 21:20:07 -0500 Received: from mail-fx0-f46.google.com ([209.85.161.46]:46502 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755188Ab1CMCUF (ORCPT ); Sat, 12 Mar 2011 21:20:05 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=vrfy.org; s=google; h=subject:from:to:cc:content-type:date:message-id:mime-version :x-mailer:content-transfer-encoding; b=LVfJU8RqlIpZMt8/QXXmE2slBLBnREEZed52EDlCG6gyTZZ2hDoFbVKKOFPovWG1x8 VwEfkqT6IwwdTyysO8dB21irX0j2/TTnHkS6oq1vb+Eb60iWn2C4biGuYFvFHU6o6yYZ i9FIS7YXX2MOVy1G/qtE9iRniJD4eC1W9NynY= Subject: [PATCH] printk: do not mangle valid userspace syslog prefixes From: Kay Sievers To: Greg KH Cc: linux-kernel , Lennart Poettering Content-Type: text/plain; charset="ISO-8859-15" Date: Sun, 13 Mar 2011 03:19:51 +0100 Message-ID: <1299982791.9769.14.camel@zag> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6113 Lines: 216 From: Kay Sievers printk: do not mangle valid userspace syslog prefixes with /dev/kmsg Log messages passed to the kernel log by using /dev/kmsg or /dev/ttyprintk might contain a syslog prefix including the syslog facility value. This makes printk to recognize these headers properly, extract the real log level from it to use, and add the prefix as a proper prefix to the log buffer, instead of wrongly printing it as the log message text. Before: $ echo '<14>text' > /dev/kmsg $ dmesg -r <4>[135159.594810] <14>text After: $ echo '<14>text' > /dev/kmsg $ dmesg -r <14>[ 50.750654] text Cc: Lennart Poettering Signed-off-by: Kay Sievers --- printk.c | 138 +++++++++++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 104 insertions(+), 34 deletions(-) diff --git a/kernel/printk.c b/kernel/printk.c index 3623152..33284ad 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -515,6 +515,71 @@ static void _call_console_drivers(unsigned start, } /* + * Parse the syslog header <[0-9]*>. The decimal value represents 32bit, the + * lower 3 bit are the log level, the rest are the log facility. In case + * userspace passes usual userspace syslog messages to /dev/kmsg or + * /dev/ttyprintk, the log prefix might contain the facility. Printk needs + * to extract the correct log level for in-kernel processing, and not mangle + * the original value. + * + * If a prefix is found, the length of the prefix is returned. If 'level' is + * passed, it will be filled in with the log level without a possible facility + * value. If 'special' is passed, the special printk prefix chars are accepted + * and returned. If no valid header is found, 0 is returned and the passed + * variables are not touched. + */ +static size_t log_prefix(const char *p, unsigned int *level, char *special) +{ + unsigned int lev = 0; + char sp = '\0'; + size_t len; + + if (p[0] != '<' || !p[1]) + return 0; + if (p[2] == '>') { + /* usual single digit level number or special char */ + switch (p[1]) { + case '0' ... '7': + lev = p[1] - '0'; + break; + case 'c': /* KERN_CONT */ + case 'd': /* KERN_DEFAULT */ + sp = p[1]; + break; + default: + return 0; + } + len = 3; + } else { + /* multi digit including the level and facility number */ + char *endp = NULL; + + if (p[1] < '0' && p[1] > '9') + return 0; + + lev = (simple_strtoul(&p[1], &endp, 10) & 7); + if (endp == NULL || endp[0] != '>') + return 0; + len = (endp + 1) - p; + } + + /* do not accept special char if not asked for */ + if (sp && !special) + return 0; + + if (special) { + *special = sp; + /* return special char, do not touch level */ + if (sp) + return len; + } + + if (level) + *level = lev; + return len; +} + +/* * Call the console drivers, asking them to write out * log_buf[start] to log_buf[end - 1]. * The console_lock must be held. @@ -529,13 +594,9 @@ static void call_console_drivers(unsigned start, unsigned end) cur_index = start; start_print = start; while (cur_index != end) { - if (msg_level < 0 && ((end - cur_index) > 2) && - LOG_BUF(cur_index + 0) == '<' && - LOG_BUF(cur_index + 1) >= '0' && - LOG_BUF(cur_index + 1) <= '7' && - LOG_BUF(cur_index + 2) == '>') { - msg_level = LOG_BUF(cur_index + 1) - '0'; - cur_index += 3; + if (msg_level < 0 && ((end - cur_index) > 2)) { + /* strip log prefix */ + cur_index += log_prefix(&LOG_BUF(cur_index), &msg_level, NULL); start_print = cur_index; } while (cur_index != end) { @@ -733,6 +794,8 @@ asmlinkage int vprintk(const char *fmt, va_list args) unsigned long flags; int this_cpu; char *p; + size_t plen; + char special; boot_delay_msec(); printk_delay(); @@ -773,45 +836,52 @@ asmlinkage int vprintk(const char *fmt, va_list args) printed_len += vscnprintf(printk_buf + printed_len, sizeof(printk_buf) - printed_len, fmt, args); - p = printk_buf; - /* Do we have a loglevel in the string? */ - if (p[0] == '<') { - unsigned char c = p[1]; - if (c && p[2] == '>') { - switch (c) { - case '0' ... '7': /* loglevel */ - current_log_level = c - '0'; - /* Fallthrough - make sure we're on a new line */ - case 'd': /* KERN_DEFAULT */ - if (!new_text_line) { - emit_log_char('\n'); - new_text_line = 1; - } - /* Fallthrough - skip the loglevel */ - case 'c': /* KERN_CONT */ - p += 3; - break; + /* Read log level and handle special printk prefix */ + plen = log_prefix(p, ¤t_log_level, &special); + if (plen) { + p += plen; + + switch (special) { + case 'c': /* Strip KERN_CONT, continue line */ + plen = 0; + break; + case 'd': /* Strip KERN_DEFAULT, start new line */ + plen = 0; + default: + if (!new_text_line) { + emit_log_char('\n'); + new_text_line = 1; } } } /* - * Copy the output into log_buf. If the caller didn't provide - * appropriate log level tags, we insert them here + * Copy the output into log_buf. If the caller didn't provide + * the appropriate log prefix, we insert them here */ - for ( ; *p; p++) { + for (; *p; p++) { if (new_text_line) { - /* Always output the token */ - emit_log_char('<'); - emit_log_char(current_log_level + '0'); - emit_log_char('>'); - printed_len += 3; new_text_line = 0; + if (plen) { + /* Copy original log prefix */ + int i; + + for (i = 0; i < plen; i++) + emit_log_char(printk_buf[i]); + printed_len += plen; + } else { + /* Add log prefix */ + emit_log_char('<'); + emit_log_char(current_log_level + '0'); + emit_log_char('>'); + printed_len += 3; + } + if (printk_time) { - /* Follow the token with the time */ + /* Add the current time stamp */ char tbuf[50], *tp; unsigned tlen; unsigned long long t; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/