re: bcache: A block layer cache

re: bcache: A block layer cache

[Dan Carpenter]

Hello Kent Overstreet,

The patch cafe56359144: "bcache: A block layer cache" from Mar 23, 
2013, leads to the following warning:
"drivers/md/bcache/util.c:92 hprint()
	 error: format string overflow. buf_size: 3 length: 4"

drivers/md/bcache/util.c
    77  ssize_t hprint(char *buf, int64_t v)
    78  {
    79          static const char units[] = "?kMGTPEZY";
    80          char dec[3] = "";
    81          int u, t = 0;
    82  
    83          for (u = 0; v >= 1024 || v <= -1024; u++) {
    84                  t = v & ~(~0 << 10);
    85                  v >>= 10;
    86          }
    87  
    88          if (!u)
    89                  return sprintf(buf, "%llu", v);
    90  
    91          if (v < 100 && v > -100)
    92                  sprintf(dec, ".%i", t / 100);

For example, hprint(buf, 2024) will cause a one char buffer overflow.

    93  
    94          return sprintf(buf, "%lli%s%c", v, dec, units[u]);

regards,
dan carpenter

Re: bcache: A block layer cache

[Dan Carpenter]

Slightly unrelated, it's weird that bcache has KEY_START() and
START_KEY().  Maybe FIRST_KEY() would be a better name for
START_KEY()?

regards,
dan carpenter

Re: bcache: A block layer cache

[Kent Overstreet]

On Mon, Apr 01, 2013 at 10:37:41PM +0300, Dan Carpenter wrote:
> Hello Kent Overstreet,
> 
> The patch cafe56359144: "bcache: A block layer cache" from Mar 23, 
> 2013, leads to the following warning:
> "drivers/md/bcache/util.c:92 hprint()
> 	 error: format string overflow. buf_size: 3 length: 4"

Thanks - fixed

commit c20bbfc0e049ca785bb19419121091e4fd419886
Author: Kent Overstreet <koverstreet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Date:   Fri Apr 5 14:12:28 2013 -0700

    bcache: Fix a format string overflow
    
    Reported-by: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
    Signed-off-by: Kent Overstreet <koverstreet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>

diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
index a9619d8..da3a99e 100644
--- a/drivers/md/bcache/util.c
+++ b/drivers/md/bcache/util.c
@@ -76,7 +76,7 @@ STRTO_H(strtoull, unsigned long long)
 ssize_t bch_hprint(char *buf, int64_t v)
 {
 	static const char units[] = "?kMGTPEZY";
-	char dec[3] = "";
+	char dec[4] = "";
 	int u, t = 0;
 
 	for (u = 0; v >= 1024 || v <= -1024; u++) {
@@ -88,7 +88,7 @@ ssize_t bch_hprint(char *buf, int64_t v)
 		return sprintf(buf, "%llu", v);
 
 	if (v < 100 && v > -100)
-		sprintf(dec, ".%i", t / 100);
+		snprintf(dec, sizeof(dec), ".%i", t / 100);
 
 	return sprintf(buf, "%lli%s%c", v, dec, units[u]);
 }