diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index dc0c8fadce1fe3a2e01cdbc22189557c1d0a465d..d321f32ed9029538f35605c9be5a5e1ff02b18f6 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -291,7 +291,7 @@ int diSync(struct inode *ipimap)
 int diRead(struct inode *ip)
 {
 	struct jfs_sb_info *sbi = JFS_SBI(ip->i_sb);
-	int iagno, ino, extno, rc;
+	int iagno, ino, extno, rc, agno;
 	struct inode *ipimap;
 	struct dinode *dp;
 	struct iag *iagp;
@@ -340,8 +340,11 @@ int diRead(struct inode *ip)
 
 	/* get the ag for the iag */
 	agstart = le64_to_cpu(iagp->agstart);
+	agno = BLKTOAG(agstart, JFS_SBI(ip->i_sb));
 
 	release_metapage(mp);
+	if (agno >= MAXAG || agno < 0)
+		return -EIO;
 
 	rel_inode = (ino & (INOSPERPAGE - 1));
 	pageno = blkno >> sbi->l2nbperpage;