linux-kernel - [PATCH] ext2: Handle fiemap on empty files to prevent EINVAL

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Message-ID: <20250612142855.2678267-1-wegao@suse.com>
Date: Thu, 12 Jun 2025 10:28:55 -0400
From: Wei Gao <wegao@...e.com>
To: linux-kernel@...r.kernel.org
Cc: jack@...e.com,
	linux-ext4@...r.kernel.org,
	wegao@...e.com
Subject: [PATCH] ext2: Handle fiemap on empty files to prevent EINVAL

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.
The new validation logic directly references ext4_fiemap_check_ranges.

Link: https://github.com/linux-test-project/ltp/issues/1246
Signed-off-by: Wei Gao <wegao@...e.com>
---
 fs/ext2/inode.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 30f8201c155f..e5cc61088f21 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -895,10 +895,30 @@ int ext2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		u64 start, u64 len)
 {
 	int ret;
+	u64 maxbytes;
 
 	inode_lock(inode);
-	len = min_t(u64, len, i_size_read(inode));
+	maxbytes = inode->i_sb->s_maxbytes;
+
+	if (len == 0) {
+		ret = -EINVAL;
+		goto unlock_inode;
+	}
+
+	if (start > maxbytes) {
+		ret = -EFBIG;
+		goto unlock_inode;
+	}
+
+	/*
+	 * Shrink request scope to what the fs can actually handle.
+	 */
+	if (len > maxbytes || (maxbytes - len) < start)
+		len = maxbytes - start;
+
 	ret = iomap_fiemap(inode, fieinfo, start, len, &ext2_iomap_ops);
+
+unlock_inode:
 	inode_unlock(inode);
 
 	return ret;
-- 
2.49.0