kmsg - properly print over-long continuation lines

Reserve PREFIX_MAX bytes in the LOG_LINE_MAX line when buffering a
continuation line, to be able to properly prefix the LOG_LINE_MAX
line with the syslog prefix and timestamp when printing it.

Reported-By: Dave Jones <davej@redhat.com>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 19 insertions, 14 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 177fa49357a5..d87ca5c6a989 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -235,7 +235,8 @@ static u32 log_next_idx;
 static u64 clear_seq;
 static u32 clear_idx;
 
-#define LOG_LINE_MAX 1024
+#define PREFIX_MAX              32
+#define LOG_LINE_MAX            1024 - PREFIX_MAX
 
 /* record buffer */
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
@@ -876,7 +877,7 @@ static size_t msg_print_text(const struct log *msg, enum log_flags prev,
 
                 if (buf) {
                         if (print_prefix(msg, syslog, NULL) +
-                            text_len + 1>= size - len)
+                            text_len + 1 >= size - len)
                                 break;
 
                         if (prefix)
@@ -907,7 +908,7 @@ static int syslog_print(char __user *buf, int size)
         struct log *msg;
         int len = 0;
 
-        text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
+        text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
         if (!text)
                 return -ENOMEM;
 
@@ -930,7 +931,8 @@ static int syslog_print(char __user *buf, int size)
 
                 skip = syslog_partial;
                 msg = log_from_idx(syslog_idx);
-                n = msg_print_text(msg, syslog_prev, true, text, LOG_LINE_MAX);
+                n = msg_print_text(msg, syslog_prev, true, text,
+                                   LOG_LINE_MAX + PREFIX_MAX);
                 if (n - syslog_partial <= size) {
                         /* message fits into buffer, move forward */
                         syslog_idx = log_next(syslog_idx);
@@ -969,7 +971,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
         char *text;
         int len = 0;
 
-        text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
+        text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
         if (!text)
                 return -ENOMEM;
 
@@ -1022,7 +1024,8 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
                         struct log *msg = log_from_idx(idx);
                         int textlen;
 
-                        textlen = msg_print_text(msg, prev, true, text, LOG_LINE_MAX);
+                        textlen = msg_print_text(msg, prev, true, text,
+                                                 LOG_LINE_MAX + PREFIX_MAX);
                         if (textlen < 0) {
                                 len = textlen;
                                 break;
@@ -1367,15 +1370,15 @@ static struct cont {
         bool flushed:1;                 /* buffer sealed and committed */
 } cont;
 
-static void cont_flush(void)
+static void cont_flush(enum log_flags flags)
 {
         if (cont.flushed)
                 return;
         if (cont.len == 0)
                 return;
 
-        log_store(cont.facility, cont.level, LOG_NOCONS, cont.ts_nsec,
-                  NULL, 0, cont.buf, cont.len);
+        log_store(cont.facility, cont.level, LOG_NOCONS | flags,
+                  cont.ts_nsec, NULL, 0, cont.buf, cont.len);
 
         cont.flushed = true;
 }
@@ -1386,7 +1389,8 @@ static bool cont_add(int facility, int level, const char *text, size_t len)
                 return false;
 
         if (cont.len + len > sizeof(cont.buf)) {
-                cont_flush();
+                /* the line gets too long, split it up in separate records */
+                cont_flush(LOG_CONT);
                 return false;
         }
 
@@ -1522,7 +1526,7 @@ asmlinkage int vprintk_emit(int facility, int level,
                  * or another task also prints continuation lines.
                  */
                 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
-                        cont_flush();
+                        cont_flush(0);
 
                 /* buffer line if possible, otherwise store it right away */
                 if (!cont_add(facility, level, text, text_len))
@@ -1540,7 +1544,7 @@ asmlinkage int vprintk_emit(int facility, int level,
                 if (cont.len && cont.owner == current) {
                         if (!(lflags & LOG_PREFIX))
                                 stored = cont_add(facility, level, text, text_len);
-                        cont_flush();
+                        cont_flush(0);
                 }
 
                 if (!stored)
@@ -1633,7 +1637,8 @@ EXPORT_SYMBOL(printk);
 
 #else
 
-#define LOG_LINE_MAX 0
+#define LOG_LINE_MAX            0
+#define PREFIX_MAX              0
 static struct cont {
         size_t len;
         size_t cons;
@@ -1938,7 +1943,7 @@ static enum log_flags console_prev;
  */
 void console_unlock(void)
 {
-        static char text[LOG_LINE_MAX];
+        static char text[LOG_LINE_MAX + PREFIX_MAX];
         static u64 seen_seq;
         unsigned long flags;
         bool wake_klogd = false;