Commit a3b5c106 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'printk-for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk 

Pull printk updates from Petr Mladek:

 - Keep spinlocks busted until the end of panic()

 - Fix races between calculating number of messages that would fit into
   user space buffers, filling the buffers, and switching printk.time
   parameter

 - Some code clean up

* tag 'printk-for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  printk: Remove print_prefix() calls with NULL buffer.
  printk: fix printk_time race.
  printk: Make printk_emit() local function.
  panic: avoid deadlocks in re-entrant console drivers
parents c6f1b355 07c17732

include/linux/printk.h

+0 −5
Original line number Diff line number Diff line
@@ -166,11 +166,6 @@ int vprintk_emit(int facility, int level, 
asmlinkage __printf(1, 0)

int vprintk(const char *fmt, va_list args);



asmlinkage __printf(5, 6) __cold

int printk_emit(int facility, int level,

		const char *dict, size_t dictlen,

		const char *fmt, ...);



asmlinkage __printf(1, 2) __cold

int printk(const char *fmt, ...);

kernel/panic.c

+5 −1
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/kmsg_dump.h>

#include <linux/kallsyms.h>

#include <linux/notifier.h>

#include <linux/vt_kern.h>

#include <linux/module.h>

#include <linux/random.h>

#include <linux/ftrace.h>
@@ -237,7 +238,10 @@ void panic(const char *fmt, ...) 
	if (_crash_kexec_post_notifiers)

		__crash_kexec(NULL);



	bust_spinlocks(0);

#ifdef CONFIG_VT

	unblank_screen();

#endif

	console_unblank();



	/*

	 * We may have ended up stopping the CPU holding the lock (in

kernel/printk/printk.c

+63 −68
Original line number Diff line number Diff line
@@ -403,6 +403,7 @@ DECLARE_WAIT_QUEUE_HEAD(log_wait); 
static u64 syslog_seq;

static u32 syslog_idx;

static size_t syslog_partial;

static bool syslog_time;



/* index and sequence number of the first record stored in the buffer */

static u64 log_first_seq;
@@ -752,6 +753,19 @@ struct devkmsg_user { 
	char buf[CONSOLE_EXT_LOG_MAX];

};



static __printf(3, 4) __cold

int devkmsg_emit(int facility, int level, const char *fmt, ...)

{

	va_list args;

	int r;



	va_start(args, fmt);

	r = vprintk_emit(facility, level, NULL, 0, fmt, args);

	va_end(args);



	return r;

}



static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)

{

	char *buf, *line;
@@ -810,7 +824,7 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from) 
		}

	}



	printk_emit(facility, level, NULL, 0, "%s", line);

	devkmsg_emit(facility, level, "%s", line);

	kfree(buf);

	return ret;

}
@@ -1213,50 +1227,39 @@ static inline void boot_delay_msec(int level) 
static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);

module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);



static size_t print_time(u64 ts, char *buf)

static size_t print_syslog(unsigned int level, char *buf)

{

	unsigned long rem_nsec;



	if (!printk_time)

		return 0;



	rem_nsec = do_div(ts, 1000000000);

	return sprintf(buf, "<%u>", level);

}



	if (!buf)

		return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);

static size_t print_time(u64 ts, char *buf)

{

	unsigned long rem_nsec = do_div(ts, 1000000000);



	return sprintf(buf, "[%5lu.%06lu] ",

		       (unsigned long)ts, rem_nsec / 1000);

}



static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)

static size_t print_prefix(const struct printk_log *msg, bool syslog,

			   bool time, char *buf)

{

	size_t len = 0;

	unsigned int prefix = (msg->facility << 3) | msg->level;



	if (syslog) {

		if (buf) {

			len += sprintf(buf, "<%u>", prefix);

		} else {

			len += 3;

			if (prefix > 999)

				len += 3;

			else if (prefix > 99)

				len += 2;

			else if (prefix > 9)

				len++;

		}

	}



	len += print_time(msg->ts_nsec, buf ? buf + len : NULL);

	if (syslog)

		len = print_syslog((msg->facility << 3) | msg->level, buf);

	if (time)

		len += print_time(msg->ts_nsec, buf + len);

	return len;

}



static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *buf, size_t size)

static size_t msg_print_text(const struct printk_log *msg, bool syslog,

			     bool time, char *buf, size_t size)

{

	const char *text = log_text(msg);

	size_t text_size = msg->text_len;

	size_t len = 0;

	char prefix[PREFIX_MAX];

	const size_t prefix_len = print_prefix(msg, syslog, time, prefix);



	do {

		const char *next = memchr(text, '\n', text_size);
@@ -1271,19 +1274,17 @@ static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *bu 
		}



		if (buf) {

			if (print_prefix(msg, syslog, NULL) +

			    text_len + 1 >= size - len)

			if (prefix_len + text_len + 1 >= size - len)

				break;



			len += print_prefix(msg, syslog, buf + len);

			memcpy(buf + len, prefix, prefix_len);

			len += prefix_len;

			memcpy(buf + len, text, text_len);

			len += text_len;

			buf[len++] = '\n';

		} else {

			/* SYSLOG_ACTION_* buffer size only calculation */

			len += print_prefix(msg, syslog, NULL);

			len += text_len;

			len++;

			len += prefix_len + text_len + 1;

		}



		text = next;
@@ -1318,9 +1319,17 @@ static int syslog_print(char __user *buf, int size) 
			break;

		}



		/*

		 * To keep reading/counting partial line consistent,

		 * use printk_time value as of the beginning of a line.

		 */

		if (!syslog_partial)

			syslog_time = printk_time;



		skip = syslog_partial;

		msg = log_from_idx(syslog_idx);

		n = msg_print_text(msg, true, text, LOG_LINE_MAX + PREFIX_MAX);

		n = msg_print_text(msg, true, syslog_time, text,

				   LOG_LINE_MAX + PREFIX_MAX);

		if (n - syslog_partial <= size) {

			/* message fits into buffer, move forward */

			syslog_idx = log_next(syslog_idx);
@@ -1360,11 +1369,13 @@ static int syslog_print_all(char __user *buf, int size, bool clear) 
	u64 next_seq;

	u64 seq;

	u32 idx;

	bool time;



	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);

	if (!text)

		return -ENOMEM;



	time = printk_time;

	logbuf_lock_irq();

	/*

	 * Find first record that fits, including all following records,
@@ -1375,7 +1386,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) 
	while (seq < log_next_seq) {

		struct printk_log *msg = log_from_idx(idx);



		len += msg_print_text(msg, true, NULL, 0);

		len += msg_print_text(msg, true, time, NULL, 0);

		idx = log_next(idx);

		seq++;

	}
@@ -1386,7 +1397,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) 
	while (len > size && seq < log_next_seq) {

		struct printk_log *msg = log_from_idx(idx);



		len -= msg_print_text(msg, true, NULL, 0);

		len -= msg_print_text(msg, true, time, NULL, 0);

		idx = log_next(idx);

		seq++;

	}
@@ -1397,14 +1408,9 @@ static int syslog_print_all(char __user *buf, int size, bool clear) 
	len = 0;

	while (len >= 0 && seq < next_seq) {

		struct printk_log *msg = log_from_idx(idx);

		int textlen;



		textlen = msg_print_text(msg, true, text,

		int textlen = msg_print_text(msg, true, time, text,

					     LOG_LINE_MAX + PREFIX_MAX);

		if (textlen < 0) {

			len = textlen;

			break;

		}



		idx = log_next(idx);

		seq++;
@@ -1528,11 +1534,14 @@ int do_syslog(int type, char __user *buf, int len, int source) 
		} else {

			u64 seq = syslog_seq;

			u32 idx = syslog_idx;

			bool time = syslog_partial ? syslog_time : printk_time;



			while (seq < log_next_seq) {

				struct printk_log *msg = log_from_idx(idx);



				error += msg_print_text(msg, true, NULL, 0);

				error += msg_print_text(msg, true, time, NULL,

							0);

				time = printk_time;

				idx = log_next(idx);

				seq++;

			}
@@ -1935,21 +1944,6 @@ asmlinkage int vprintk(const char *fmt, va_list args) 
}

EXPORT_SYMBOL(vprintk);



asmlinkage int printk_emit(int facility, int level,

			   const char *dict, size_t dictlen,

			   const char *fmt, ...)

{

	va_list args;

	int r;



	va_start(args, fmt);

	r = vprintk_emit(facility, level, dict, dictlen, fmt, args);

	va_end(args);



	return r;

}

EXPORT_SYMBOL(printk_emit);



int vprintk_default(const char *fmt, va_list args)

{

	int r;
@@ -2005,6 +1999,7 @@ EXPORT_SYMBOL(printk); 


#define LOG_LINE_MAX		0

#define PREFIX_MAX		0

#define printk_time		false



static u64 syslog_seq;

static u32 syslog_idx;
@@ -2028,8 +2023,8 @@ static void console_lock_spinning_enable(void) { } 
static int console_lock_spinning_disable_and_check(void) { return 0; }

static void call_console_drivers(const char *ext_text, size_t ext_len,

				 const char *text, size_t len) {}

static size_t msg_print_text(const struct printk_log *msg,

			     bool syslog, char *buf, size_t size) { return 0; }

static size_t msg_print_text(const struct printk_log *msg, bool syslog,

			     bool time, char *buf, size_t size) { return 0; }

static bool suppress_message_printing(int level) { return false; }



#endif /* CONFIG_PRINTK */
@@ -2387,8 +2382,7 @@ skip: 


		len += msg_print_text(msg,

				console_msg_format & MSG_FORMAT_SYSLOG,

				text + len,

				sizeof(text) - len);

				printk_time, text + len, sizeof(text) - len);

		if (nr_ext_console_drivers) {

			ext_len = msg_print_ext_header(ext_text,

						sizeof(ext_text),
@@ -3112,7 +3106,7 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog, 
		goto out;



	msg = log_from_idx(dumper->cur_idx);

	l = msg_print_text(msg, syslog, line, size);

	l = msg_print_text(msg, syslog, printk_time, line, size);



	dumper->cur_idx = log_next(dumper->cur_idx);

	dumper->cur_seq++;
@@ -3183,6 +3177,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, 
	u32 next_idx;

	size_t l = 0;

	bool ret = false;

	bool time = printk_time;



	if (!dumper->active)

		goto out;
@@ -3206,7 +3201,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, 
	while (seq < dumper->next_seq) {

		struct printk_log *msg = log_from_idx(idx);



		l += msg_print_text(msg, true, NULL, 0);

		l += msg_print_text(msg, true, time, NULL, 0);

		idx = log_next(idx);

		seq++;

	}
@@ -3217,7 +3212,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, 
	while (l > size && seq < dumper->next_seq) {

		struct printk_log *msg = log_from_idx(idx);



		l -= msg_print_text(msg, true, NULL, 0);

		l -= msg_print_text(msg, true, time, NULL, 0);

		idx = log_next(idx);

		seq++;

	}
@@ -3230,7 +3225,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, 
	while (seq < dumper->next_seq) {

		struct printk_log *msg = log_from_idx(idx);



		l += msg_print_text(msg, syslog, buf + l, size - l);

		l += msg_print_text(msg, syslog, time, buf + l, size - l);

		idx = log_next(idx);

		seq++;

	}

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