[PATCH v2] ext2: Handle fiemap on empty files to prevent EINVAL

[Wei Gao <wegao@suse.com>]

Previously, ext2_fiemap would unconditionally apply "len = min_t(u64, len,
i_size_read(inode));", When inode->i_size was 0 (for an empty file), this
would reduce the requested len to 0. Passing len = 0 to iomap_fiemap could
then result in an -EINVAL error, even for valid queries on empty files.

Link: https://github.com/linux-test-project/ltp/issues/1246
Signed-off-by: Wei Gao <wegao@suse.com>
---
 fs/ext2/inode.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 30f8201c155f..591db2b4390a 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -895,9 +895,15 @@ int ext2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		u64 start, u64 len)
 {
 	int ret;
+	u64 i_size;
 
 	inode_lock(inode);
-	len = min_t(u64, len, i_size_read(inode));
+
+	i_size = i_size_read(inode);
+
+	if (i_size > 0)
+		len = min_t(u64, len, i_size_read(inode));
+
 	ret = iomap_fiemap(inode, fieinfo, start, len, &ext2_iomap_ops);
 	inode_unlock(inode);
 
-- 
2.49.0