[JFFS2] fix race condition in jffs2_lzo_compress()
Geert Uytterhoeven [Wed, 5 Nov 2008 22:21:16 +0000 (23:21 +0100)]
deflate_mutex protects the globals lzo_mem and lzo_compress_buf.  However,
jffs2_lzo_compress() unlocks deflate_mutex _before_ it has copied out the
compressed data from lzo_compress_buf.  Correct this by moving the mutex
unlock after the copy.

In addition, document what deflate_mutex actually protects.

Cc: stable@kernel.org
Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Acked-by: Richard Purdie <rpurdie@openedhand.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

fs/jffs2/compr_lzo.c

index 47b0457..90cb60d 100644 (file)
@@ -19,7 +19,7 @@
 
 static void *lzo_mem;
 static void *lzo_compress_buf;
-static DEFINE_MUTEX(deflate_mutex);
+static DEFINE_MUTEX(deflate_mutex);    /* for lzo_mem and lzo_compress_buf */
 
 static void free_workspace(void)
 {
@@ -49,18 +49,21 @@ static int jffs2_lzo_compress(unsigned char *data_in, unsigned char *cpage_out,
 
        mutex_lock(&deflate_mutex);
        ret = lzo1x_1_compress(data_in, *sourcelen, lzo_compress_buf, &compress_size, lzo_mem);
-       mutex_unlock(&deflate_mutex);
-
        if (ret != LZO_E_OK)
-               return -1;
+               goto fail;
 
        if (compress_size > *dstlen)
-               return -1;
+               goto fail;
 
        memcpy(cpage_out, lzo_compress_buf, compress_size);
-       *dstlen = compress_size;
+       mutex_unlock(&deflate_mutex);
 
+       *dstlen = compress_size;
        return 0;
+
+ fail:
+       mutex_unlock(&deflate_mutex);
+       return -1;
 }
 
 static int jffs2_lzo_decompress(unsigned char *data_in, unsigned char *cpage_out,