jfs: Fix FITRIM argument handling

Currently when 'range->start' is beyond the end of file system
nothing is done and that fact is ignored, where in fact we should return
EINVAL. The same problem is when 'range.len' is smaller than file system
block.

Fix this by adding check for such conditions and return EINVAL
appropriately.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Acked-by: Tino Reichardt <milky-kernel@mcmilk.de>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>

fs/jfs/jfs_discard.c

@@ -83,7 +83,7 @@ int jfs_ioc_trim(struct inode *ip, struct fstrim_range *range)
 	struct bmap *bmp = JFS_SBI(ip->i_sb)->bmap;
 	struct super_block *sb = ipbmap->i_sb;
 	int agno, agno_end;
-	s64 start, end, minlen;
+	u64 start, end, minlen;
 	u64 trimmed = 0;
 
 	/**
@@ -93,15 +93,19 @@ int jfs_ioc_trim(struct inode *ip, struct fstrim_range *range)
 	 * minlen:	minimum extent length in Bytes
 	 */
 	start = range->start >> sb->s_blocksize_bits;
-	if (start < 0)
-		start = 0;
 	end = start + (range->len >> sb->s_blocksize_bits) - 1;
-	if (end >= bmp->db_mapsize)
-		end = bmp->db_mapsize - 1;
 	minlen = range->minlen >> sb->s_blocksize_bits;
-	if (minlen <= 0)
+	if (minlen == 0)
 		minlen = 1;
 
+	if (minlen > bmp->db_agsize ||
+	    start >= bmp->db_mapsize ||
+	    range->len < sb->s_blocksize)
+		return -EINVAL;
+
+	if (end >= bmp->db_mapsize)
+		end = bmp->db_mapsize - 1;
+
 	/**
 	 * we trim all ag's within the range
 	 */