1 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index de7f55682088..1be23d9fdacb 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1302,15 +1302,21 @@ static inline int jbd_space_needed(journal_t *journal)
 
 extern int jbd_blocks_per_page(struct inode *inode);
 
+/* JBD uses a CRC32 checksum */
+#define JBD_MAX_CHECKSUM_SIZE 4
+
 static inline u32 jbd2_chksum(journal_t *journal, u32 crc,
                               const void *address, unsigned int length)
 {
         struct {
                 struct shash_desc shash;
-                char ctx[crypto_shash_descsize(journal->j_chksum_driver)];
+                char ctx[JBD_MAX_CHECKSUM_SIZE];
         } desc;
         int err;
 
+        BUG_ON(crypto_shash_descsize(journal->j_chksum_driver) >
+                JBD_MAX_CHECKSUM_SIZE);
+
         desc.shash.tfm = journal->j_chksum_driver;
         desc.shash.flags = 0;
         *(u32 *)desc.ctx = crc;