[PATCH 01/15] ovl: add permission hooks outside of do_splice_direct()

Amir Goldstein
2023-11-14T15:33:04Z

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.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/overlayfs/copy_up.c | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 4382881b0709..106f8643af3b 100644
--- 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,
--
2.34.1