From 6c322f5cf7476ded7a9a20f7be72462065a03c68 Mon Sep 17 00:00:00 2001 From: Frank Sorenson Date: Sat, 22 Aug 2026 16:55:17 -0500 Subject: [PATCH] cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0 With len == 0 (clone to EOF), the effective length is computed as: len = src_inode->i_size - off; If off > i_size, this is a negative loff_t, corrupting the ByteCount in the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range in filemap_write_and_wait_range(). The existing off >= i_size check fires only after the ioctl has already been sent. Snapshot i_size_read() once for both the bounds check and the length calculation, eliminating the TOCTOU and 32-bit torn-read risk. Reject off > src_size with -EINVAL. Treat off == src_size as a no-op, consistent with __generic_remap_file_range_prep(). Fixes: 04b38d601239 ("vfs: pull btrfs clone API to vfs layer") Cc: stable@vger.kernel.org Signed-off-by: Frank Sorenson Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara --- fs/smb/client/cifsfs.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c index 2073b29ff969..7ecd70efdfea 100644 --- a/fs/smb/client/cifsfs.c +++ b/fs/smb/client/cifsfs.c @@ -1413,8 +1413,19 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off, */ lock_two_nondirectories(target_inode, src_inode); - if (len == 0) - len = src_inode->i_size - off; + if (len == 0) { + loff_t src_size = i_size_read(src_inode); + + if (off > src_size) { + rc = -EINVAL; + goto unlock; + } + len = src_size - off; + if (!len) { + rc = 0; + goto unlock; + } + } cifs_dbg(FYI, "clone range\n");