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author | Kay Sievers <kay.sievers@vrfy.org> | 2011-03-13 03:19:51 +0100 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-03-14 08:49:16 -0700 |
commit | 9d90c8d9cde929cbc575098e825d7c29d9f45054 (patch) | |
tree | 49cd83812a9cbbb40cb0c6b73b13455cad0029ea /kernel/printk.c | |
parent | 54fad532b29aa9145f12a83f4f82820c2f23b4e2 (diff) | |
download | lwn-9d90c8d9cde929cbc575098e825d7c29d9f45054.tar.gz lwn-9d90c8d9cde929cbc575098e825d7c29d9f45054.zip |
printk: do not mangle valid userspace syslog prefixes
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 <lennart@poettering.net>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'kernel/printk.c')
-rw-r--r-- | kernel/printk.c | 138 |
1 files changed, 104 insertions, 34 deletions
diff --git a/kernel/printk.c b/kernel/printk.c index 2ddbdc73aade..5e3d042e7001 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -499,6 +499,71 @@ 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. @@ -513,13 +578,9 @@ 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) { @@ -717,6 +778,8 @@ 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(); @@ -757,45 +820,52 @@ 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 <c> KERN_CONT, continue line */ + plen = 0; + break; + case 'd': /* Strip <d> 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; |