[Qemu-block] [PATCH 1/2] blkdebug: Catch bs->exact_filename overflow

[Max Reitz]

The bs->exact_filename field may not be sufficient to store the full
blkdebug node filename. In this case, we should not generate a filename
at all instead of an unusable one.

Cc: address@hidden
Reported-by: Qu Wenruo <address@hidden>
Signed-off-by: Max Reitz <address@hidden>
---
 block/blkdebug.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/block/blkdebug.c b/block/blkdebug.c
index a5196e8..6166d6a 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -840,9 +840,13 @@ static void blkdebug_refresh_filename(BlockDriverState 
*bs, QDict *options)
     }
 
     if (!force_json && bs->file->bs->exact_filename[0]) {
-        snprintf(bs->exact_filename, sizeof(bs->exact_filename),
-                 "blkdebug:%s:%s", s->config_file ?: "",
-                 bs->file->bs->exact_filename);
+        int ret = snprintf(bs->exact_filename, sizeof(bs->exact_filename),
+                           "blkdebug:%s:%s", s->config_file ?: "",
+                           bs->file->bs->exact_filename);
+        if (ret >= sizeof(bs->exact_filename)) {
+            /* An overflow makes the filename unusable, so do not report any */
+            bs->exact_filename[0] = 0;
+        }
     }
 
     opts = qdict_new();
-- 
2.9.4