From bf567e9488c0241cd58c13ef998b208a7f8a58f3 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Sun, 1 Feb 2026 21:21:59 +0000
Subject: [PATCH] sparse-random: Clamp preferred block size

The preferred block size must be between 512 and 32M.  It was possible
to set a larger block size, so we must clamp it.  (I clamped it at
both ends, even though currently the smallest block size is 1024).

Fixes: commit 5612598a49aaf4ac49f1b3e096dc4945ea7df640
(cherry picked from commit 7a7a103b0711a89a1912d6768db4a91bec3a5f17)
---
 plugins/sparse-random/sparse-random.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/plugins/sparse-random/sparse-random.c b/plugins/sparse-random/sparse-random.c
index 8d1c2944..3d7da426 100644
--- a/plugins/sparse-random/sparse-random.c
+++ b/plugins/sparse-random/sparse-random.c
@@ -285,7 +285,15 @@ sparse_random_block_size (void *handle,
                           uint32_t *maximum)
 {
   *minimum = 1;
-  *preferred = blocksize;
+
+  /* Preferred blocksize must be 512..32M so clamp this value. */
+  if (blocksize < 512)
+    *preferred = 512;
+  else if (blocksize > 32*1024*1024)
+    *preferred = 32*1024*1024;
+  else
+    *preferred = blocksize;
+
   *maximum = 0xffffffff;
   return 0;
 }
-- 
2.47.3