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printk: do not mangle valid userspace syslog prefixes

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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>
This commit is contained in:
Kay Sievers 2011-03-13 03:19:51 +01:00 committed by Greg Kroah-Hartman
parent 54fad532b2
commit 9d90c8d9cd
1 changed files with 104 additions and 34 deletions
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138
kernel/printk.c
View File

@ -498,6 +498,71 @@ 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].
@ -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, &current_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;