ext4: no need to remove extent if len is 0 in ext4_es_remove_extent()
len is 0 means no extent needs to be removed, so return immediately.
Otherwise it could trigger the following BUG_ON() in
ext4_es_remove_extent()
end = lblk + len - 1;
BUG_ON(end < lblk);
This could be reproduced by a simple truncate(1) command by an
unprivileged user
truncate -s $(($((2**32 - 1)) * 4096)) /mnt/ext4/testfile
The same is true for __es_insert_extent().
Patched kernel passed xfstests regression test.
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 9f1380e..f768f4a 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -456,6 +456,9 @@
es_debug("add [%u/%u) %llu %llx to extent status tree of inode %lu\n",
lblk, len, pblk, status, inode->i_ino);
+ if (!len)
+ return 0;
+
BUG_ON(end < lblk);
newes.es_lblk = lblk;
@@ -649,6 +652,9 @@
es_debug("remove [%u/%u) from extent status tree of inode %lu\n",
lblk, len, inode->i_ino);
+ if (!len)
+ return err;
+
end = lblk + len - 1;
BUG_ON(end < lblk);