[PATCH 06/15] remap_range: move permission hooks out of do_clone_file_range()

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

In many of the vfs helpers, file permission hook is called before
taking sb_start_write(), making them "start-write-safe".
do_clone_file_range() is an exception to this rule.

do_clone_file_range() has two callers - vfs_clone_file_range() and
overlayfs. Move remap_verify_area() checks from do_clone_file_range()
out to vfs_clone_file_range() to make them "start-write-safe".

Overlayfs already has calls to rw_verify_area() with the same security
permission hooks as remap_verify_area() has.
The rest of the checks in remap_verify_area() are irrelevant for
overlayfs that calls do_clone_file_range() offset 0 and positive length.

This is needed for fanotify "pre content" events.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/remap_range.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/remap_range.c b/fs/remap_range.c
index 87ae4f0dc3aa..42f79cb2b1b1 100644
--- a/fs/remap_range.c
+++ b/fs/remap_range.c
@@ -385,14 +385,6 @@ loff_t do_clone_file_range(struct file *file_in, loff_t pos_in,
if (!file_in->f_op->remap_file_range)
return -EOPNOTSUPP;

- ret = remap_verify_area(file_in, pos_in, len, false);
- if (ret)
- return ret;
-
- ret = remap_verify_area(file_out, pos_out, len, true);
- if (ret)
- return ret;
-
ret = file_in->f_op->remap_file_range(file_in, pos_in,
file_out, pos_out, len, remap_flags);
if (ret < 0)
@@ -410,6 +402,14 @@ loff_t vfs_clone_file_range(struct file *file_in, loff_t pos_in,
{
loff_t ret;

+ ret = remap_verify_area(file_in, pos_in, len, false);
+ if (ret)
+ return ret;
+
+ ret = remap_verify_area(file_out, pos_out, len, true);
+ if (ret)
+ return ret;
+
file_start_write(file_out);
ret = do_clone_file_range(file_in, pos_in, file_out, pos_out, len,
remap_flags);
--
2.34.1