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 ff028315f12bd0b6a6f2bdc19245e27df4131ce2..82b1613a012fdabf835a1d263fe0b2a688a388c6 100644 (file)
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1096,23 +1096,8 @@ 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) +