[PATCH] f2fs: validate MOVE_RANGE destination size

[Wenjie Qi]

F2FS_IOC_MOVE_RANGE checks the source range, but not the destination end
before updating i_size. A source hole can expose this: __clone_blkaddrs()
skips NULL_ADDR entries and returns success, so the caller can still extend
the destination inode with unchecked pos_out + len.

Reject destination overflow and use inode_newsize_ok() before extending
the destination inode.

Fixes: 4dd6f977fc77 ("f2fs: support an ioctl to move a range of data blocks")
Cc: stable@xxxxxxxxxx
Assisted-by: Codex:gpt-5.5
Signed-off-by: Wenjie Qi <qiwenjie@xxxxxxxxxx>
---
 fs/f2fs/file.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 4b52c56d71f0..2a5c6f741f56 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -3121,8 +3121,9 @@ static int f2fs_move_file_range(struct file *file_in, loff_t pos_in,
 	struct inode *dst = file_inode(file_out);
 	struct f2fs_sb_info *sbi = F2FS_I_SB(src);
 	struct f2fs_lock_context lc;
-	size_t olen = len, dst_max_i_size = 0;
-	size_t dst_osize;
+	size_t olen = len;
+	loff_t dst_max_i_size = 0;
+	loff_t dst_osize, dst_end;
 	int ret;
 
 	if (file_in->f_path.mnt != file_out->f_path.mnt ||
@@ -3179,8 +3180,15 @@ static int f2fs_move_file_range(struct file *file_in, loff_t pos_in,
 	}
 
 	dst_osize = dst->i_size;
-	if (pos_out + olen > dst->i_size)
-		dst_max_i_size = pos_out + olen;
+	if (olen > LLONG_MAX - pos_out)
+		goto out_unlock;
+	dst_end = pos_out + olen;
+	if (dst_end > dst->i_size) {
+		ret = inode_newsize_ok(dst, dst_end);
+		if (ret)
+			goto out_unlock;
+		dst_max_i_size = dst_end;
+	}
 
 	/* verify the end result is block aligned */
 	if (!IS_ALIGNED(pos_in, F2FS_BLKSIZE) ||
-- 
2.43.0