printk() - restore prefix/timestamp printing for multi-newline strings

Calls like:
  printk("\n *** DEADLOCK ***\n\n");
will print 3 properly indented, separated, syslog + timestamp prefixed lines in
the log output.

Reported-By: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/printk.c b/kernel/printk.c
index c42faf97404adea0ecbce13efb63afcb0254ab5a..915a8be10b5fd4f74b2bbea08fa88415b5244d18 100644 (file)
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -448,7 +448,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 
        /* escape non-printable characters */
        for (i = 0; i < msg->text_len; i++) {
-               char c = log_text(msg)[i];
+               unsigned char c = log_text(msg)[i];
 
                if (c < ' ' || c >= 128)
                        len += sprintf(user->buf + len, "\\x%02x", c);
@@ -461,7 +461,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
                bool line = true;
 
                for (i = 0; i < msg->dict_len; i++) {
-                       char c = log_dict(msg)[i];
+                       unsigned char c = log_dict(msg)[i];
 
                        if (line) {
                                user->buf[len++] = ' ';
@@ -785,56 +785,81 @@ static bool printk_time;
 #endif
 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 
-static size_t prepend_timestamp(unsigned long long t, char *buf)
+static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
 {
-       unsigned long rem_ns;
+       size_t len = 0;
 
-       if (!printk_time)
-               return 0;
+       if (syslog) {
+               if (buf) {
+                       len += sprintf(buf, "<%u>", msg->level);
+               } else {
+                       len += 3;
+                       if (msg->level > 9)
+                               len++;
+                       if (msg->level > 99)
+                               len++;
+               }
+       }
 
-       if (!buf)
-               return 15;
+       if (printk_time) {
+               if (buf) {
+                       unsigned long long ts = msg->ts_nsec;
+                       unsigned long rem_nsec = do_div(ts, 1000000000);
 
-       rem_ns = do_div(t, 1000000000);
+                       len += sprintf(buf + len, "[%5lu.%06lu] ",
+                                        (unsigned long) ts, rem_nsec / 1000);
+               } else {
+                       len += 15;
+               }
+       }
 
-       return sprintf(buf, "[%5lu.%06lu] ",
-                      (unsigned long) t, rem_ns / 1000);
+       return len;
 }
 
-static int syslog_print_line(u32 idx, char *text, size_t size)
+static size_t msg_print_text(const struct log *msg, bool syslog,
+                            char *buf, size_t size)
 {
-       struct log *msg;
-       size_t len;
+       const char *text = log_text(msg);
+       size_t text_size = msg->text_len;
+       size_t len = 0;
 
-       msg = log_from_idx(idx);
-       if (!text) {
-               /* calculate length only */
-               len = 3;
+       do {
+               const char *next = memchr(text, '\n', text_size);
+               size_t text_len;
 
-               if (msg->level > 9)
-                       len++;
-               if (msg->level > 99)
-                       len++;
-               len += prepend_timestamp(0, NULL);
+               if (next) {
+                       text_len = next - text;
+                       next++;
+                       text_size -= next - text;
+               } else {
+                       text_len = text_size;
+               }
 
-               len += msg->text_len;
-               len++;
-               return len;
-       }
+               if (buf) {
+                       if (print_prefix(msg, syslog, NULL) +
+                           text_len + 1>= size - len)
+                               break;
+
+                       len += print_prefix(msg, syslog, buf + 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 + 1;
+               }
+
+               text = next;
+       } while (text);
 
-       len = sprintf(text, "<%u>", msg->level);
-       len += prepend_timestamp(msg->ts_nsec, text + len);
-       if (len + msg->text_len > size)
-               return -EINVAL;
-       memcpy(text + len, log_text(msg), msg->text_len);
-       len += msg->text_len;
-       text[len++] = '\n';
        return len;
 }
 
 static int syslog_print(char __user *buf, int size)
 {
        char *text;
+       struct log *msg;
        int len;
 
        text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
@@ -847,7 +872,8 @@ static int syslog_print(char __user *buf, int size)
                syslog_seq = log_first_seq;
                syslog_idx = log_first_idx;
        }
-       len = syslog_print_line(syslog_idx, text, LOG_LINE_MAX);
+       msg = log_from_idx(syslog_idx);
+       len = msg_print_text(msg, true, text, LOG_LINE_MAX);
        syslog_idx = log_next(syslog_idx);
        syslog_seq++;
        raw_spin_unlock_irq(&logbuf_lock);
@@ -887,14 +913,18 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
                seq = clear_seq;
                idx = clear_idx;
                while (seq < log_next_seq) {
-                       len += syslog_print_line(idx, NULL, 0);
+                       struct log *msg = log_from_idx(idx);
+
+                       len += msg_print_text(msg, true, NULL, 0);
                        idx = log_next(idx);
                        seq++;
                }
                seq = clear_seq;
                idx = clear_idx;
                while (len > size && seq < log_next_seq) {
-                       len -= syslog_print_line(idx, NULL, 0);
+                       struct log *msg = log_from_idx(idx);
+
+                       len -= msg_print_text(msg, true, NULL, 0);
                        idx = log_next(idx);
                        seq++;
                }
@@ -904,9 +934,10 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
 
                len = 0;
                while (len >= 0 && seq < next_seq) {
+                       struct log *msg = log_from_idx(idx);
                        int textlen;
 
-                       textlen = syslog_print_line(idx, text, LOG_LINE_MAX);
+                       textlen = msg_print_text(msg, true, text, LOG_LINE_MAX);
                        if (textlen < 0) {
                                len = textlen;
                                break;
@@ -1044,7 +1075,9 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
                        seq = syslog_seq;
                        idx = syslog_idx;
                        while (seq < log_next_seq) {
-                               error += syslog_print_line(idx, NULL, 0);
+                               struct log *msg = log_from_idx(idx);
+
+                               error += msg_print_text(msg, true, NULL, 0);
                                idx = log_next(idx);
                                seq++;
                        }
@@ -1439,10 +1472,8 @@ static struct log *log_from_idx(u32 idx) { return NULL; }
 static u32 log_next(u32 idx) { return 0; }
 static char *log_text(const struct log *msg) { return NULL; }
 static void call_console_drivers(int level, const char *text, size_t len) {}
-static size_t prepend_timestamp(unsigned long long t, char *buf)
-{
-       return 0;
-}
+static size_t msg_print_text(const struct log *msg, bool syslog,
+                            char *buf, size_t size) { return 0; }
 
 #endif /* CONFIG_PRINTK */
 
@@ -1750,7 +1781,7 @@ again:
        for (;;) {
                struct log *msg;
                static char text[LOG_LINE_MAX];
-               size_t len, l;
+               size_t len;
                int level;
 
                raw_spin_lock_irqsave(&logbuf_lock, flags);
@@ -1771,13 +1802,7 @@ again:
                msg = log_from_idx(console_idx);
                level = msg->level & 7;
 
-               len = prepend_timestamp(msg->ts_nsec, text);
-               l = msg->text_len;
-               if (len + l + 1 >= sizeof(text))
-                       l = sizeof(text) - len - 1;
-               memcpy(text + len, log_text(msg), l);
-               len += l;
-               text[len++] = '\n';
+               len = msg_print_text(msg, false, text, sizeof(text));
 
                console_idx = log_next(console_idx);
                console_seq++;