queue-6.1/ext2-handle-fiemap-on-empty-files-to-prevent-einval.patch

From 88ad21037a432016c652ae659c30629ea88bdd31 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Fri, 13 Jun 2025 11:18:38 -0400
Subject: ext2: Handle fiemap on empty files to prevent EINVAL

From: Wei Gao <wegao@suse.com>

[ Upstream commit a099b09a3342a0b28ea330e405501b5b4d0424b4 ]

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>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250613152402.3432135-1-wegao@suse.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ext2/inode.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 5a32fcd55183..430ccd983491 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -860,9 +860,19 @@ int ext2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		u64 start, u64 len)
 {
 	int ret;
+	loff_t i_size;
 
 	inode_lock(inode);
-	len = min_t(u64, len, i_size_read(inode));
+	i_size = i_size_read(inode);
+	/*
+	 * iomap_fiemap() returns EINVAL for 0 length. Make sure we don't trim
+	 * length to 0 but still trim the range as much as possible since
+	 * ext2_get_blocks() iterates unmapped space block by block which is
+	 * slow.
+	 */
+	if (i_size == 0)
+		i_size = 1;
+	len = min_t(u64, len, i_size);
 	ret = iomap_fiemap(inode, fieinfo, start, len, &ext2_iomap_ops);
 	inode_unlock(inode);
 
-- 
2.39.5