udf: Do not bother merging very long extents

commit 53cafe1d6d8ef9f93318e5bfccc0d24f27d41ced upstream.

When merging very long extents we try to push as much length as possible
to the first extent. However this is unnecessarily complicated and not
really worth the trouble. Furthermore there was a bug in the logic
resulting in corrupting extents in the file as syzbot reproducer shows.
So just don't bother with the merging of extents that are too long
together.

CC: stable@vger.kernel.org
Reported-by: syzbot+60f291a24acecb3c2bd5@syzkaller.appspotmail.com
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 4c7a1c1e03d32d09aadabae282c7e57375b5d1db..a8539897a9fcac911636ff42e3e688fd74d86b20 100644 (file)
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1093,23 +1093,8 @@ static void udf_merge_extents(struct inode *inode, struct kernel_long_ad *laarr,
                        blocksize - 1) >> blocksize_bits)))) {
 
                        if (((li->extLength & UDF_EXTENT_LENGTH_MASK) +
-                               (lip1->extLength & UDF_EXTENT_LENGTH_MASK) +
-                               blocksize - 1) & ~UDF_EXTENT_LENGTH_MASK) {
-                               lip1->extLength = (lip1->extLength -
-                                                 (li->extLength &
-                                                  UDF_EXTENT_LENGTH_MASK) +
-                                                  UDF_EXTENT_LENGTH_MASK) &
-                                                       ~(blocksize - 1);
-                               li->extLength = (li->extLength &
-                                                UDF_EXTENT_FLAG_MASK) +
-                                               (UDF_EXTENT_LENGTH_MASK + 1) -
-                                               blocksize;
-                               lip1->extLocation.logicalBlockNum =
-                                       li->extLocation.logicalBlockNum +
-                                       ((li->extLength &
-                                               UDF_EXTENT_LENGTH_MASK) >>
-                                               blocksize_bits);
-                       } else {
+                            (lip1->extLength & UDF_EXTENT_LENGTH_MASK) +
+                            blocksize - 1) <= UDF_EXTENT_LENGTH_MASK) {
                                li->extLength = lip1->extLength +
                                        (((li->extLength &
                                                UDF_EXTENT_LENGTH_MASK) +