ovl: add permission hooks outside of do_splice_direct()

The main callers of do_splice_direct() also call rw_verify_area() for
the entire range that is being copied, e.g. by vfs_copy_file_range()
or do_sendfile() before calling do_splice_direct().

The only caller that does not have those checks for entire range is
ovl_copy_up_file().  In preparation for removing the checks inside
do_splice_direct(), add rw_verify_area() call in ovl_copy_up_file().

For extra safety, perform minimal sanity checks from rw_verify_area()
for non negative offsets also in the copy up do_splice_direct() loop
without calling the file permission hooks.

This is needed for fanotify "pre content" events.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231122122715.2561213-2-amir73il@gmail.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 4382881b070948cc21425c330153db7eebd065a0..106f8643af3bb28da5a1f60f0bba442eb36e315c 100644 (file)
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -230,6 +230,19 @@ static int ovl_copy_fileattr(struct inode *inode, const struct path *old,
        return ovl_real_fileattr_set(new, &newfa);
 }
 
+static int ovl_verify_area(loff_t pos, loff_t pos2, loff_t len, loff_t totlen)
+{
+       loff_t tmp;
+
+       if (WARN_ON_ONCE(pos != pos2))
+               return -EIO;
+       if (WARN_ON_ONCE(pos < 0 || len < 0 || totlen < 0))
+               return -EIO;
+       if (WARN_ON_ONCE(check_add_overflow(pos, len, &tmp)))
+               return -EIO;
+       return 0;
+}
+
 static int ovl_copy_up_file(struct ovl_fs *ofs, struct dentry *dentry,
                            struct file *new_file, loff_t len)
 {
@@ -244,13 +257,20 @@ static int ovl_copy_up_file(struct ovl_fs *ofs, struct dentry *dentry,
        int error = 0;
 
        ovl_path_lowerdata(dentry, &datapath);
-       if (WARN_ON(datapath.dentry == NULL))
+       if (WARN_ON_ONCE(datapath.dentry == NULL) ||
+           WARN_ON_ONCE(len < 0))
                return -EIO;
 
        old_file = ovl_path_open(&datapath, O_LARGEFILE | O_RDONLY);
        if (IS_ERR(old_file))
                return PTR_ERR(old_file);
 
+       error = rw_verify_area(READ, old_file, &old_pos, len);
+       if (!error)
+               error = rw_verify_area(WRITE, new_file, &new_pos, len);
+       if (error)
+               goto out_fput;
+
        /* Try to use clone_file_range to clone up within the same fs */
        ovl_start_write(dentry);
        cloned = do_clone_file_range(old_file, 0, new_file, 0, len, 0);
@@ -309,6 +329,10 @@ static int ovl_copy_up_file(struct ovl_fs *ofs, struct dentry *dentry,
                        }
                }
 
+               error = ovl_verify_area(old_pos, new_pos, this_len, len);
+               if (error)
+                       break;
+
                ovl_start_write(dentry);
                bytes = do_splice_direct(old_file, &old_pos,
                                         new_file, &new_pos,