block: use dynamically sized probe buffer in libblkid-tiny

This fixes label extraction on vfat partitions with large cluster sizes,
the previous statically sized buffer of 4096 bytes was too small.

diff --git a/libblkid-tiny/libblkid-tiny.c b/libblkid-tiny/libblkid-tiny.c
index bd86c4196cca7395a46afe8f27e69d88aa20fdb8..623ef6947fe5958af4affbfd043b07913d61572d 100644 (file)
--- a/libblkid-tiny/libblkid-tiny.c
+++ b/libblkid-tiny/libblkid-tiny.c
@@ -13,6 +13,7 @@
 int blkid_debug_mask = 0;
 
 static unsigned char *probe_buffer;
+static unsigned int probe_buffer_size = 0;
 
 int get_linux_version (void)
 {
@@ -80,17 +81,24 @@ unsigned char *blkid_probe_get_buffer(blkid_probe pr,
                                blkid_loff_t off, blkid_loff_t len)
 {
        int ret;
+       unsigned char *buf;
 
-       if (len > 4096) {
-               fprintf(stderr, "probe buffer too small %d\n", (int) len);
-               return NULL;
-       }
+       if (len > probe_buffer_size) {
+               buf = realloc(probe_buffer, len);
+
+               if (!buf) {
+                       fprintf(stderr, "failed to allocate %d byte buffer\n",
+                               (int)len);
 
-       if (!probe_buffer) {
-               probe_buffer = malloc(4096);
-               memset(probe_buffer, 0, 4096);
+                       return NULL;
+               }
+
+               probe_buffer = buf;
+               probe_buffer_size = len;
        }
 
+       memset(probe_buffer, 0, probe_buffer_size);
+
        lseek(pr->fd, off, SEEK_SET);
        ret = read(pr->fd, probe_buffer, len);