[Qemu-block] [PATCH v2] qcow2: Prevent backing file names longer than 1023

[Max Reitz]

We reject backing file names with a length of more than 1023 characters
when opening a qcow2 file, so we should not produce such files
ourselves.

Cc: address@hidden
Signed-off-by: Max Reitz <address@hidden>
---
v2:
- Move the check to qcow2_change_backing_file() so the BDS state will
  not be modified if that condition is not met [Kevin]
---
 block/qcow2.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/qcow2.c b/block/qcow2.c
index 056525c..470734b 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1986,6 +1986,10 @@ static int qcow2_change_backing_file(BlockDriverState 
*bs,
 {
     BDRVQcow2State *s = bs->opaque;
 
+    if (backing_file && strlen(backing_file) > 1023) {
+        return -EINVAL;
+    }
+
     pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_file ?: "");
     pstrcpy(bs->backing_format, sizeof(bs->backing_format), backing_fmt ?: "");
 
-- 
2.8.0